Connacht's five-match winning run came to an end as Cardiff Blues triumphed 36-30 at Arms Park.
In an error-ridden game, Blues were deserved winners, scoring three tries through Olly Robinson, Matthew Morgan and Owen Lane.
Jarrod Evans kicked three penalties and a conversion with his replacement, Gareth Anscombe, adding two conversions and two penalties.
Shane Delahunt scored two tries for Connacht, Niyi Adeolokun and John Muldoon one each, with Jack Carty kicking two penalties and a conversion and Steve Crosbie a single conversion.
Connacht dominated the opening period with centre, Tom Farrell, making a neat break to test the home defence.
However, resolute tackling from Blues kept their line intact before Carty put the visitors ahead with a penalty after 12 minutes.
Evans soon responded with a penalty before the hosts took the lead with an excellent try. Willis Halaholo ran strongly to feed Macauley Cook, who made ground before Halaholo was again involved to send Robinson over.
Evans converted before adding a penalty as ill-discipline and careless errors began to creep into Connacht's game.
However, it was Blues who made a major error that put the Irish side back in contention.
After his side won a line-out on half-way, Halaholo's telegraphed pass was picked off by Adeolokun, who raced 45 metres to score.
Carty converted and added a penalty but a third penalty from Evans was enough to give Blues a 16-13 half-time lead.
After the restart, Connacht pounded their opponents' line with a succession of attacking scrums but despite seeming to have the dominant eight, they were surprisingly penalised to relieve the pressure.
Another big decision soon went against the visitors when centre, Eoin Griffin, was sin-binned for a deliberate knock on before Blues introduced Anscombe in place of Evans at fly-half.
The home side capitalised on Griffin's absence when, from a five-metre scrum, Morgan ran cleverly to score his side's second try.
Soon afterwards, Blues had another ruled out for blocking from Nick Williams prior to Tom James running 40 metres to send Anscombe over.
Griffin still had not returned when Connacht scored their second try as Delahunt finished off a driving line-out.
Griffin was replaced by Pita Ahki before Blues sealed the game when Anscombe darted through a gap to create a try for young wing Lane.
Anscombe's conversion gave Blues a 30-18 lead going into the final quarter.
With 10 minutes remaining, Williams was sin-binned before Delahunt again finished off a line-out drive for his second before Anscombe kicked two penalties.
The visitors picked up a bonus point when Muldoon crossed to give Blues some nervous moments.