Key Biscayne, April 6:

Serena Williams screamed at herself, broke her racket and then finally finished off Jelena Jankovic 6-1, 5-7, 6-3 for her fifth title at the Sony Ericsson Open.

Williams survived some shaky play down the stretch and an improbable comeback by Jankovic, who trailed 5-3 in the second set. Williams closed out the elusive victory on her eighth championship point with an overhead slam. Both players held up well in the 29-degree Celsius sunshine and some of their best rallies — one lasting 26 shots — came in the final few games.

Williams also won the tournament in 2002-04 and 2007. She matched Steffi Graf’s record of five women’s titles here, while Andre Agassi won the tournament six times. Williams improved to 14-1 this year, with her only loss to Jankovic in the quarter-finals at the Australian Open.

Williams dominated for a set and a half, and she was three points from victory in the second set when she began spraying nervous shots, while Jankovic started to play better. Williams lost her serve at love for 5-all, then double-faulted to lose set point and forced a third set.

Williams raced to a 5-0 lead in the third set but again wavered. She had her first championship point in the next game, another at 5-1 and three more at 5-2. Williams twice exhorted herself with screams but lost that game, then slammed her racket against the concrete and sent it skipping into the side wall.

Jankovic saved two more match points in the next game before Williams closed out the victory with her 51st winner. She also had 52 errors. Williams won $590,000. Jankovic received $295,675.