Bellamy, who is expected to confirm his retirement next week, opened the scoring at the Cardiff City Stadium on Sunday with a deflected 15th-minute effort.
The Welsh club led at the interval but second-half strikes from substitute Andre Schurrle and striker Fernando Torres - with his first league goal since January - produced a turnaround in Chelsea's favour.
The result means Ole Gunnar Solskjaer's already-relegated side finish bottom of the table, two points behind Fulham.
Chelsea end the campaign in third spot, four points adrift of champions Manchester City.
Solskjaer made two changes to his side after the 3-0 defeat at Newcastle last time out confirmed Cardiff's relegation. Bellamy and Mats Moeller Daehli replaced Bo-Kyung Kim and Wilfried Zaha.
After the 0-0 draw at home to Norwich last Sunday, Jose Mourinho made six changes to Chelsea's starting line-up. Torres, Eden Hazard and Tomas Kalas were promoted from the bench having been subs against the Canaries, while Oscar, Cesar Azpilicueta and John Obi Mikel all returned to action.
Ashley Cole captained the Blues on what could be his final appearance in the absence of John Terry (knock) and Frank Lampard (illness), both of whom are reportedly pondering contract extensions on reduced terms.
In the early stages, Steven Caulker made a superb recovery to stretch out a leg and block Torres' goalbound effort. After Caulker's initial error, goalkeeper David Marshall had dashed out of his balloon-strewn area but Torres took the ball round him, only to see Caulker deny him on the line.
Cardiff then took the lead in the 15th minute. Bellamy collected a pass in the left channel from Peter Whittingham 25 yards out, and let fly with a left-footed shot that deflected in past Mark Schwarzer off the back of Azpilicueta.
It was Cardiff's first goal in open play for more than five hours, but it might yet be credited to Chelsea's right-back as the initial shot could have been heading wide.
Mohamed Salah was guilty of missing several good chances in the first half, while Oscar and Hazard each failed to convert passes from Cole.
Fraizer Campbell fired over after a mazy run for Cardiff, while Mikel, booked for a cynical trip on Daehli, avoided a second yellow card for another on Fabio as a disjointed first half came to an end.
After the break, Torres blasted wide and Declan John shot straight at Schwarzer at the other end. Hazard then fired into the side-netting after a slick Chelsea move.
Schurrle came off the bench in the 66th minute and equalised six minutes later with his eighth Premier League goal of the season.
The goal was harsh on Marshall, who made a truly brilliant initial stop to deny Azpilicueta who had stolen into the area to meet Oscar's left-wing cross with a header.
The close-range follow-up effort from the Spaniard hit the crossbar - but the rebound fell to Schurrle, who volleyed the ball into the turf and then saw it go in.
Then three minutes later, poor defending from Cardiff allowed Chelsea to forge ahead.
After Azpilicueta's cross, Fabio played Torres onside as the ball dropped from a header by Schurrle to the feet of the Spaniard, who turned and tucked away an easy finish for only his fifth league goal of the campaign.
That proved to be the last goal of the contest, with Hazard unable to net a Schurrle cross at the far post and Marshall subsequently saving well from the Germany forward.
After the final whistle, both teams applauded their supporters as they signed off for the summer and began to turn their thoughts towards squad rebuilding.