Six and a half hours after lifting the Venus Rosewater Dish for the fifth time, Serena teamed up with her 32-year-old sibling to down Czech sixth seeds Andrea Hlavackova and Lucie Hradecka 7-5 6-4.
Venus, a first-round loser in singles, fired an ace to complete the 78-minute victory on a floodlit arena just 10 minutes before the 11pm cut-off time for Centre Court play.
It was a fifth All England Club doubles title for the duo, and 13th overall.
After watching Serena, 30, win her three-set battle against Agnieszka Radwanska in the singles, Venus was delighted to play an active role on court and at one point produced a stunning volley despite falling on to her bottom.
"I felt I played a match with her earlier so I felt like it was my second match too," a beaming Venus said after accepting the doubles trophy in the Royal Box. "It was a great day for all of us."
"If anyone knows what that (winning the singles and doubles here on the same day) feels like, it's me. It's an amazing feeling."