The Partenopei hit the post late on as they pushed for the winner which would secure a Champions League play-off spot but the Nerazzurri held on for a point
Benitez endured a troublesome six-month spell in charge of the Nerazzurri giants in 2010, which ended when he was unceremoniously sacked despite winning the Club World Cup, but he could easily have enjoyed a victory against his former employers.
An even first half saw both sides create numerous chances, but Napoli forward Jose Callejon was wasteful at one end, while goalkeeper Jose Reina was rarely troubled and the Spaniard was alert when he was called into action.
Napoli went close again at the start of the second half, as Jorginho was denied in the 50th minute.
Gonzalo Higuain had his chances and Gokhan Inler struck a post in the final 20 minutes, but Napoli were forced to accept a draw which ensured they stay eight points ahead of Fiorentina in the race for Champions League football with three Serie A games remaining.
There was concern for Napoli late on, when striker Higuain was carried off with an ankle injury following a challenge with Marco Andreolli and Benitez will be hoping it does not prove to be serious.
Fifth-placed Inter, whose coach Walter Mazzarri was also facing his former club, are now six points off Parma and AC Milan as they attempt to secure a Europa League place.
Benitez's quest for revenge almost got off to the perfect start, when Callejon latched on to a left-wing cross in the first minute but his looping effort went back across goal and dropped wide.
Mazzarri saw his men grow into the game with some crisp passing in midfield, but they could only threaten from long range, as Mateo Kovacic shot agonisingly wide before Reina palmed away Hernanes' stinging drive.
Dries Mertens presented Callejon with a glorious chance 13 minutes in, but the former Real Madrid man poked the Belgium winger's low cross wide from just six yards.
Callejon's miss was nearly compounded by a Napoli sending off when Miguel Angel Britos tripped Rodrigo Palacio in the 26th minute, but the Uruguayan escaped with just a yellow card despite being the last man.
Napoli remained solid at the back until the break and then showed renewed attacking intent at the start of the second period.
In the 50th minute the visitors went close twice in quick succession as Yuto Nagatomo blocked Higuain’s close-range volley, before Samir Handanovic tipped Jorginho’s effort around the post.
Inter went straight down the other end and almost broke the deadlock themselves, but Palacio could only head across the face of goal after beating Reina to Nagatomo’s cross.
A moment of brilliance from Higuain in the 72nd minute saw the Argentina forward turn Andreolli on the edge of the area before bursting into the area, but he then inexcusably blasted over the crossbar.
Inler almost snatched a late win when his effort eight minutes from time struck the right-hand post, but the visitors were unable to secure a winner and suffered a late blow when Higuain was forced off with an ankle injury following a 50-50 challenge with Andreolli.