"Happy birthday Rajni! Wishing you good health and many more achievements in life…happiness and prosperity always," Amitabh posted on micro-blogging site Twitter.
The two actors have worked together in films like "Andhaa Kanoon", "Geraftaar" and "Hum".
"It’s Happy Birthday for Rajinikanth…friend and colleague and a humble gentleman, despite his immense following and cult iconic figure," added Big B, 69.
Amitabh shares a close friendship with Rajinikanth, and was immensely concerned when the latter was admitted to the hospital for recurrent respiratory infection and gastro-intestinal problems in May this year.
Rajinikanth, who has been out of action due to his illness, will return with "Kochadaiyyan", which will be the directorial debut of his daughter, Soundarya Ashwin Rajinikanth.