The league leader blew the chance to move 12 points clear of second-place Manchester City after losing for the third time in four games in all competitions on Saturday lunchtime.
Alex Scott struck a 74th-minute winner at the Emirates to pile pressure on Arsenal ahead of next week's top-of-the-table clash at City.
Mikel Arteta's team has played two more games than City, who could close the gap to six points if they beat Chelsea on Sunday at Stamford Bridge.
Arsenal's form appears to be slipping at a crucial point of the season. Defeats to City in the League Cup final and second-division Southampton in the FA Cup have ended their pursuit of a quadruple of trophies.
They won 1-0 in the Champions League against Sporting Lisbon on Tuesday, but the latest loss will only heighten tension in the race for the title after three straight years of finishing runner-up in England's top flight.
Arteta had urged the 60,000 Arsenal fans to bring their "breakfast, lunch and dinner" and create a hostile atmosphere for the early kick-off which so often lends itself to being subdued.
But his rallying call did not translate to the pitch and his lethargic players found themselves chasing the game against a side who were in action for the first time in three weeks.
Bournemouth went ahead inside 17 minutes through Junior Kroupi's close-range goal.Â
Viktor Gyokeres levelled matters from the penalty spot in the 35th, but Arsenal struggled to create openings and Scott sealed the victory that has potentially blown the title race open.
Bournemouth have now won in back-to-back seasons at Arsenal and set a new club record run of going 12 games unbeaten in the Premier League.
With AP
9°C