Then we can just pick a new place for that center point, and transform that back into a non-overlapping position for the original rectangle. This lets us resolve the collision in one pass, touching the x coordinate only once and the y coordinate only once.

if(first.Bounds.IntersectsWith(second.Bounds) == false) return; // Compute the center of each rectangle: var firstCenter = new PointF( first.Left + first.Width /2f, first.Top + first.Height /2f ); var secondCenter = new PointF(second.Left + second.Width /2f, second.Top + second.Height/2f); // Compute the offset from the second's center to the first. var offset = firstCenter - secondCenter; // Clamp this offset to the closest point on the enlarged second // rectangle's perimeter. First horizontally... if (Math.Abs(offset.x) < (first.Width + second.Width)/2f) offset.x = Math.Sign(offset.x) * (first.Width + second.Width)/2f; // ...then vertically. if (Math.Abs(offset.y) < (first.Height + second.Height)/2f) offset.y = Math.Sign(offset.y) * (first.Height + second.Height)/2f); // Now form the top-left corner of the first rectangle at // this new position. var corner = new PointF(secondCenter.x + offset.x - first.Width /2f, secondCenter.y + offset.y - first.Height/2f); first.SetPosition(corner); 

Then we can just pick a new place for that center point, and transform that back into a non-overlapping position for the original rectangle. This lets us resolve the collision in one pass, touching only x or y, and only once - rather than stacking a vertical collision resolution after a horizontal resolution using outdated info.

We call this the "minimum translation vector" - using the smallest adjustment possible to remove the overlap, whether that's horizontal or vertical.

if(first.Bounds.IntersectsWith(second.Bounds) == false) return; // Compute the center of each rectangle: var firstCenter = new PointF( first.Left + first.Width /2f, first.Top + first.Height /2f ); var secondCenter = new PointF(second.Left + second.Width /2f, second.Top + second.Height/2f); // Compute the offset from the second's center to the first. var offset = firstCenter - secondCenter; // Compute how deeply we're overlapping, horizontally and vertically. var penetration = new PointF((first.Width + second.Width )/2f,   (first.Height - second.Height)/2f);   - new PointF(Math.Abs(offset.x), Math.Abs(offset.y)); if ( penetration.y <= 0 || (penetration.x > 0 && penetration.x < penetration.y)) { // If we're only overlapping on the x, // or we're overlapping on the x less than on the y,   // then correct our x position for the minimum safe correction. offset.x = Math.Sign(offset.x) * (first.Width  + second.Width )/2f; } else {  // Otherwise, our minimum safe correction is vertical. offset.y = Math.Sign(offset.y) * (first.Height + second.Height)/2f; } // Now form the top-left corner of the first rectangle at // this new position. var corner = new PointF(secondCenter.x + offset.x - first.Width /2f, secondCenter.y + offset.y - first.Height/2f); first.SetPosition(corner);