diff --git a/AXStretchableHeaderTabViewController.podspec b/AXStretchableHeaderTabViewController.podspec
index f97c5b4..124eec6 100644
--- a/AXStretchableHeaderTabViewController.podspec
+++ b/AXStretchableHeaderTabViewController.podspec
@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name             = "AXStretchableHeaderTabViewController"
-  s.version          = "0.1.9"
+  s.version          = "0.2.0"
   s.summary          = "Stretchable header view + Horizontal swipable tab view."
   s.description      = <<-DESC
                        Stretchable header view + Horizontal swipable tab view
diff --git a/CHANGELOG.md b/CHANGELOG.md
index ecc1e08..553f31f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # AXStretchableHeaderTabViewController CHANGELOG
 
+## 0.2.0
+
+Feature: The KVO is available for selectedIndex and selectedViewController properties.
+
 ## 0.1.9
 
 Feature: AXStretchableSubViewControllerViewSource protocol is available to set scroll view.
diff --git a/Classes/AXStretchableHeaderTabViewController.m b/Classes/AXStretchableHeaderTabViewController.m
index 760f167..2839e9e 100644
--- a/Classes/AXStretchableHeaderTabViewController.m
+++ b/Classes/AXStretchableHeaderTabViewController.m
@@ -5,6 +5,8 @@
 
 #import "AXStretchableHeaderTabViewController.h"
 
+static NSString * const AXStretchableHeaderTabViewControllerSelectedIndexKey = @"selectedIndex";
+
 @interface AXStretchableHeaderTabViewController ()
 
 @end
@@ -82,7 +84,7 @@ - (void)setSelectedViewController:(UIViewController *)selectedViewController
     return;
   }
   if (newIndex != _selectedIndex) {
-    _selectedIndex = newIndex;
+    [self changeSelectedIndex:newIndex];
   }
 }
 
@@ -132,7 +134,9 @@ - (void)setViewControllers:(NSArray *)viewControllers
     
     // tab bar
     [_tabBar setSelectedItem:[_tabBar.items firstObject]];
-    _selectedIndex = 0;
+    if (_selectedIndex != 0) {
+      [self changeSelectedIndex:0];
+    }
   }
 }
 
@@ -285,9 +289,12 @@ - (void)scrollViewDidScroll:(UIScrollView *)scrollView
 {
   if (scrollView.isDragging) {
     NSUInteger numberOfViewControllers = _viewControllers.count;
-    _selectedIndex = round(scrollView.contentOffset.x / scrollView.contentSize.width * numberOfViewControllers);
-    _selectedIndex = MIN(numberOfViewControllers - 1, MAX(0, _selectedIndex));
-    [_tabBar setSelectedItem:_tabBar.items[_selectedIndex]];
+    NSInteger newSelectedIndex = round(scrollView.contentOffset.x / scrollView.contentSize.width * numberOfViewControllers);
+    newSelectedIndex = MIN(numberOfViewControllers - 1, MAX(0, newSelectedIndex));
+    if (_selectedIndex != newSelectedIndex) {
+      [_tabBar setSelectedItem:_tabBar.items[newSelectedIndex]];
+      [self changeSelectedIndex:newSelectedIndex];
+    }
   }
 }
 
@@ -301,8 +308,11 @@ - (BOOL)tabBar:(AXTabBar *)tabBar shouldSelectItem:(UITabBarItem *)item
 
 - (void)tabBar:(UITabBar *)tabBar didSelectItem:(UITabBarItem *)item
 {
-  _selectedIndex = [[tabBar items] indexOfObject:item];
-  [_containerView setContentOffset:(CGPoint){_selectedIndex * CGRectGetWidth(_containerView.bounds), _containerView.contentOffset.y} animated:YES];
+  NSInteger newSelectedIndex = [[tabBar items] indexOfObject:item];
+  if (_selectedIndex != newSelectedIndex) {
+    [_containerView setContentOffset:(CGPoint){newSelectedIndex * CGRectGetWidth(_containerView.bounds), _containerView.contentOffset.y} animated:YES];
+    [self changeSelectedIndex:newSelectedIndex];
+  }
 }
 
 #pragma mark - Private Method
@@ -318,4 +328,13 @@ - (UIScrollView *)scrollViewWithSubViewController:(UIViewController *)viewContro
   }
 }
 
+- (void)changeSelectedIndex:(NSInteger)selectedIndex
+{
+  [self willChangeValueForKey:@"selectedIndex"];
+  [self willChangeValueForKey:@"selectedViewController"];
+  _selectedIndex = selectedIndex;
+  [self didChangeValueForKey:@"selectedIndex"];
+  [self didChangeValueForKey:@"selectedViewController"];
+}
+
 @end