"Congratulations to @MahaBJP unit for surpassing 50 lakh (5 million) membership count. Join us..." Shah tweeted.
The party has already crossed the 5-crore members mark, which is halfway to its target of inducting 10 crore members by March 31.
BJP had launched its ambitious membership drive on November 1 with Prime Minister Narendra Modi taking its first membership, followed by Shah.
The drive is aimed at making the saffron outfit the largest political party in the world with the highest number of members.