The Italy forward scored both second-half goals for second-placed Roma and was handed a mobile phone by one of the coaching staff to mark the leveller.
The 38-year-old held the phone up and took a photo with the Roma fans behind him as his side recovered from 2-0 down.
Lazio led after Stefano Mauri converted Felipe Anderson's cross, before the latter doubled the lead from 20 yards.
Totti, who has now scored 11 times against Lazio, said: "I thought about it during the week.
"Although it's in fashion, I don't usually take them because I want my private life to stay that way, but this was a special occasion, something to be remembered for a long time."
Roma went into the game knowing victory would take them above Juventus, ahead of the champions' trip to fourth-placed Napoli later on Sunday.
But it was Lazio, starting the match in third place, who opened up a 2-0 half-time lead.
Totti reduced the arrears with a fine angled strike three minutes after the restart and claimed his second from close range just after the hour to set up a tense finale.
It was his 239th goal in Serie A. Silvio Piola holds the record with 274.
Roma captain Francesco Totti took a selfie of himself to celebrate becoming the joint top scorer in the capital derby with the equaliser in a 2-2 draw against Lazio.