Alongside partner Ons Jabeur, the pair beat Sara Sorribes Tormo and Marie Bouzkova 2-6, 6-3, 13-11.
The 23-time grand slam singles champion had not played since she sustained an injury to her right leg at Wimbledon last summer.
It sparked rumours of retirement but a shock announcement last Tuesday saw Williams reveal she had been given a wild card into SW19 and would begin her preparations by playing doubles at Devonshire Park.
The 40-year-old made a slow start but she soon got into the groove and hit an array of winners sprinkled with a handful of aces.
"It was so fun to play with Ons," Williams said on-court.
"It was great. We had a lot of fun and our opponents played amazing. We were happy to stay in there.
"I called Ons, she has been playing so well and I knew I needed to play some matches and she has always been so nice to me on tour.
"Yeah, I caught some fire behind me, it was good."
Williams walked out to Irene Cara’s What A Feeling for what was her third Eastbourne appearance having previously played in the singles event back in 1998 and 2011.
Sporting white Nike trainers and three black patches on her right cheek, she was predictably rusty in the opening exchanges but was well backed by a Centre Court crowd who were watching their fifth match of the day.
The veteran served first and her 90mph effort earned an opening point after Sorribes Tormo’s reply sailed long.
It was followed by a shanked forehand, but partner Jabeur received a high-five after some excellent net play ensured the duo started with a hold.
Williams was tested out some more when Bouzkova’s wide serve proved too far out of reach and a prime opportunity for a winner went begging when the American smashed into the net.
A break did occur in the third service game, with the range of the seven-time Wimbledon winner just off after another volleyed effort landed well beyond the baseline.
Up against a pair who recently won a doubles tournament in Istanbul, it was perhaps no surprise to see Williams and Jabeur struggling and the former let out a big shriek after she was unable to get low enough to Sorribes Tormo’s shot.
When Bouzkova was able to split the duo with a winner soon after, a second break was sealed.
It took 25 minutes before Williams graced Eastbourne with a winner and her smashed volley into the ground landed in the North Stand to ensure one spectator was able to leave with a souvenir.
Her next notable action was to applaud the net play of Sorribes Tormo after the Spaniard’s drop shot wrapped up the first set in just over half an hour.
The more experienced doubles duo were able to break again in the third game of the second but Williams’ agility was noticeably improving, despite a scream being let out after she could not return a third volley in quick succession.
Sorribes Tormo’s double-fault got the set back on serve, but the breaks kept coming.
A first ace for Williams failed to thwart another break but her excellent backhand winner at the net ensured they hit back, minutes after audible gasps from the crowd when the 40-year-old slipped rushing into the net.
With the confidence flowing, another Williams volleyed winner clinched a big hold and the power of her forehand was too much in the next game to give her and Jabeur the initiative.
Williams set up a set point with a superb backhand winner from the baseline after a big ‘I got it call’ and levelled up proceedings with a 102mph ace.
A 10-point tie-breaker was required to find a winner with plenty of empty seats now the clock had ticked past 8pm.
Those left remained noisy and they were rewarded when Williams showed no lack of desire to dive to her right to make a volley which could not be returned and set up match point.
It was followed by a dramatic back and forth tie-breaker which saw Jabeur inexplicably find the net with the court at her mercy.
The Tunisian world number three made amends to set up another match point with a deft drop shot and Sorribes Tormo miscued her volley at the net to ensure the new team started with a win.
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