diff --git a/core/src/main/java/hudson/model/AbstractProject.java b/core/src/main/java/hudson/model/AbstractProject.java
index 8b46d0cd0a7e..ad7f2f9f7830 100644
--- a/core/src/main/java/hudson/model/AbstractProject.java
+++ b/core/src/main/java/hudson/model/AbstractProject.java
@@ -1100,16 +1100,27 @@ public CauseOfBlockage getCauseOfBlockage() {
 
     /**
      * Returns the project if any of the downstream project is either
-     * building, waiting, pending or buildable.
+     * building, or queued and not blocked by an upstream/downstream project build.
      * <p>
      * This means eventually there will be an automatic triggering of
      * the given project (provided that all builds went smoothly.)
      */
     public AbstractProject getBuildingDownstream() {
-        Set<Task> unblockedTasks = Jenkins.get().getQueue().getUnblockedTasks();
+        // Unblocked downstream tasks must block this project.
+        Set<Task> tasks = Jenkins.get().getQueue().getUnblockedTasks();
+        // Blocked downstream tasks must block this project.
+        // Projects blocked by upstream or downstream builds
+        // are ignored to break deadlocks.
+        for (Queue.Item item : Jenkins.get().getQueue().getBlockedItems()) {
+            if (item.getCauseOfBlockage() instanceof AbstractProject.BecauseOfUpstreamBuildInProgress ||
+                    item.getCauseOfBlockage() instanceof AbstractProject.BecauseOfDownstreamBuildInProgress) {
+                continue;
+            }
+            tasks.add(item.task);
+        }
 
         for (AbstractProject tup : getTransitiveDownstreamProjects()) {
-            if (tup != this && (tup.isBuilding() || unblockedTasks.contains(tup)))
+            if (tup != this && (tup.isBuilding() || tasks.contains(tup)))
                 return tup;
         }
         return null;
@@ -1117,16 +1128,27 @@ public AbstractProject getBuildingDownstream() {
 
     /**
      * Returns the project if any of the upstream project is either
-     * building or is in the queue.
+     * building, or queued and not blocked by an upstream/downstream project build.
      * <p>
      * This means eventually there will be an automatic triggering of
      * the given project (provided that all builds went smoothly.)
      */
     public AbstractProject getBuildingUpstream() {
-        Set<Task> unblockedTasks = Jenkins.get().getQueue().getUnblockedTasks();
+        // Unblocked upstream tasks must block this project.
+        Set<Task> tasks = Jenkins.get().getQueue().getUnblockedTasks();
+        // Blocked upstream tasks must block this project.
+        // Projects blocked by upstream or downstream builds
+        // are ignored to break deadlocks.
+        for (Queue.Item item : Jenkins.get().getQueue().getBlockedItems()) {
+            if (item.getCauseOfBlockage() instanceof AbstractProject.BecauseOfUpstreamBuildInProgress ||
+                    item.getCauseOfBlockage() instanceof AbstractProject.BecauseOfDownstreamBuildInProgress) {
+                continue;
+            }
+            tasks.add(item.task);
+        }
 
         for (AbstractProject tup : getTransitiveUpstreamProjects()) {
-            if (tup != this && (tup.isBuilding() || unblockedTasks.contains(tup)))
+            if (tup != this && (tup.isBuilding() || tasks.contains(tup)))
                 return tup;
         }
         return null;
diff --git a/test/src/test/java/hudson/model/QueueTest.java b/test/src/test/java/hudson/model/QueueTest.java
index 85ba24bbc4df..e38f9d92dcc2 100644
--- a/test/src/test/java/hudson/model/QueueTest.java
+++ b/test/src/test/java/hudson/model/QueueTest.java
@@ -568,6 +568,111 @@ public void upstreamDownstreamCycle() throws Exception {
         assertThat("The cycle should have been defanged and chain3 executed", queue.getItem(chain3), nullValue());
     }
 
+
+    @TestExtension({"upstreamProjectsInQueueBlock", "downstreamProjectsInQueueBlock"})
+    public static class BlockingQueueTaskDispatcher extends QueueTaskDispatcher {
+
+        public static final String NAME_OF_BLOCKED_PROJECT = "blocked project";
+
+        @Override
+        public CauseOfBlockage canRun(hudson.model.Queue.Item item) {
+            if (item.task.getOwnerTask().getDisplayName().equals(NAME_OF_BLOCKED_PROJECT)) {
+                return new CauseOfBlockage() {
+
+                    @Override
+                    public String getShortDescription() {
+                        return NAME_OF_BLOCKED_PROJECT + " is permanently blocked.";
+                    }
+
+                };
+            }
+            return super.canRun(item);
+        }
+
+    }
+
+    private void waitUntilWaitingListIsEmpty(Queue q) throws InterruptedException {
+        boolean waitingItemsPresent = true;
+        while (waitingItemsPresent) {
+            waitingItemsPresent = false;
+            for (Queue.Item i : q.getItems()) {
+                if (i instanceof WaitingItem) {
+                    waitingItemsPresent = true;
+                    break;
+                }
+            }
+            Thread.sleep(1000);
+        }
+    }
+
+    @Issue("JENKINS-68780")
+    @Test
+    public void upstreamProjectsInQueueBlock() throws Exception {
+
+       FreeStyleProject a = r.createFreeStyleProject(BlockingQueueTaskDispatcher.NAME_OF_BLOCKED_PROJECT);
+       FreeStyleProject b = r.createFreeStyleProject();
+       a.getPublishersList().add(new BuildTrigger(b.getName(), true));
+       b.setBlockBuildWhenUpstreamBuilding(true);
+
+       r.jenkins.rebuildDependencyGraph();
+
+       a.scheduleBuild(0, new UserIdCause());
+
+       Queue q = r.jenkins.getQueue();
+
+       waitUntilWaitingListIsEmpty(q);
+
+       b.scheduleBuild(0, new UserIdCause());
+
+       waitUntilWaitingListIsEmpty(q);
+
+       // This call is necessary because the queue blocks projects
+       // at first only temporarily. By calling the maintain method
+       // all temporarily blocked projects either become buildable or
+       // become permanently blocked
+       q.scheduleMaintenance().get();
+
+       assertEquals("Queue should contain two blocked items but didn't.", 2, q.getBlockedItems().size());
+
+       //Ensure orderly shutdown
+       q.clear();
+       r.waitUntilNoActivity();
+    }
+
+    @Issue("JENKINS-68780")
+    @Test
+    public void downstreamProjectsInQueueBlock() throws Exception {
+
+       FreeStyleProject a = r.createFreeStyleProject();
+       FreeStyleProject b = r.createFreeStyleProject(BlockingQueueTaskDispatcher.NAME_OF_BLOCKED_PROJECT);
+       a.getPublishersList().add(new BuildTrigger(b.getName(), true));
+       a.setBlockBuildWhenDownstreamBuilding(true);
+
+       r.jenkins.rebuildDependencyGraph();
+
+       b.scheduleBuild(0, new UserIdCause());
+
+       Queue q = r.jenkins.getQueue();
+
+       waitUntilWaitingListIsEmpty(q);
+
+       a.scheduleBuild(0, new UserIdCause());
+
+       waitUntilWaitingListIsEmpty(q);
+
+       // This call is necessary because the queue blocks projects
+       // at first only temporarily. By calling the maintain method
+       // all temporarily blocked projects either become buildable or
+       // become permanently blocked
+       q.scheduleMaintenance().get();
+
+       assertEquals("Queue should contain two blocked items but didn't.", 2, q.getBlockedItems().size());
+
+       //Ensure orderly shutdown
+       q.clear();
+       r.waitUntilNoActivity();
+    }
+
     public static class TestFlyweightTask extends TestTask implements Queue.FlyweightTask {
         Executor exec;
         private final Label assignedLabel;
diff --git a/war/src/main/webapp/help/project-config/block-downstream-building.html b/war/src/main/webapp/help/project-config/block-downstream-building.html
index 441d6c51b20b..9b1cfdae21bf 100644
--- a/war/src/main/webapp/help/project-config/block-downstream-building.html
+++ b/war/src/main/webapp/help/project-config/block-downstream-building.html
@@ -1,3 +1,6 @@
 <div>
  When this option is checked, Jenkins will prevent the project from building when a child of this project is in the queue, or building. The children include the direct as well as the transitive children.
 </div>
+<div>
+ However, if projects are circular dependent on each other, Jenkins will break the cycle by starting with the oldest requested build from the cycle.
+</div>
\ No newline at end of file
diff --git a/war/src/main/webapp/help/project-config/block-downstream-building_de.html b/war/src/main/webapp/help/project-config/block-downstream-building_de.html
new file mode 100644
index 000000000000..0df022fb3280
--- /dev/null
+++ b/war/src/main/webapp/help/project-config/block-downstream-building_de.html
@@ -0,0 +1,8 @@
+<div>
+    Wenn angewählt, verhindert das Bauen des Projekts, solange sich ein nachgelagertes Projekt in
+    der Build-Warteschlange befindet oder gerade gebaut wird. Dabei werden sowohl
+    direkte als auch transitive Abhängigkeiten berücksichtigt.
+</div>
+<div>
+    Jedoch werden Verklemmung von zirkulär abhängigen Projekten aufgelöst, indem der älteste angeforderte Build begonnen wird.
+</div>
\ No newline at end of file
diff --git a/war/src/main/webapp/help/project-config/block-upstream-building.html b/war/src/main/webapp/help/project-config/block-upstream-building.html
index cee2b6248169..2e39c7410209 100644
--- a/war/src/main/webapp/help/project-config/block-upstream-building.html
+++ b/war/src/main/webapp/help/project-config/block-upstream-building.html
@@ -1,3 +1,6 @@
 <div>
  When this option is checked, Jenkins will prevent the project from building when a dependency of this project is in the queue, or building. The dependencies include the direct as well as the transitive dependencies.
 </div>
+<div>
+ However, if projects are circular dependent on each other, Jenkins will break the cycle by starting with the oldest requested build from the cycle.
+</div>
diff --git a/war/src/main/webapp/help/project-config/block-upstream-building_de.html b/war/src/main/webapp/help/project-config/block-upstream-building_de.html
index 72ca4bae984b..25fead38c291 100644
--- a/war/src/main/webapp/help/project-config/block-upstream-building_de.html
+++ b/war/src/main/webapp/help/project-config/block-upstream-building_de.html
@@ -3,3 +3,6 @@
     der Build-Warteschlange befindet oder gerade gebaut wird. Dabei werden sowohl
     direkte als auch transitive Abhängigkeiten berücksichtigt.
 </div>
+<div>
+    Jedoch werden Verklemmung von zirkulär abhängigen Projekten aufgelöst, indem der älteste angeforderte Build begonnen wird.
+</div>
\ No newline at end of file