Lazio raced into a first-half lead through a familiar source in Ciro Immobile and the Lazio forward will not score many better goals than his 25th-minute volley.
However, Pasquale Schiattarella's strike on the stroke of half-time, another well-taken volley, levelled the scores.
The hosts, who had Schiattarella sent off in stoppage time, had the better of the chances to win it but had to settle for a draw.
After just one win in their last six games in all competitions, Lazio are languishing eighth in Serie A, with Benevento in 13th.
This was only the second meeting between the Inzaghi brothers as coaches. Simone won the previous encounter, when Lazio beat Bologna, then coached by Filippo, in December 2018.
Simone looked to be on course to make it two wins from two after Immobile's brilliant strike -- his 11th goal in his last 11 appearances for Lazio.
Once again, however, Lazio's backline -- which has kept just one clean sheet since the opening day of the season in all competitions -- was breached, and they were fortunate not concede another late in the match.