Paul Ranger and Filip Kuba also scored for the Lightning, who have a 12-game winning streak against Pittsburgh. Tampa Bay coach John Tortorella earned his 200th victory with the Lightning.
Richards has helped set up 12 goals during an eight-game assist streak. His goal 1:31 into the third gave Tampa Bay a 4-1 lead.
Lecavalier's short-handed goal later in the period moved him within one of tying Brain Bradley's team record, set during the 1992-93 season.
Sergei Gonchar scored for the Penguins, who lost for only the fourth time in 19 games.