Garryowen went into this game at Dooradoyle with a clear mission to end their three-match losing sequence at the venue.
Three away wins had them in mid-table in Ulster Bank League Division 1A but the home hoodoo had to be broken and at the end of an ebb and flow contest they managed just that.
Out-half Darragh Fitzpatrick threatened to spoil matters for the home side when he landed an early penalty for Blackrock but his opposite number Declan Cusack replied for the Light Blues.
Centre Rob Keogh kicked 'Rock's second penalty to push them 6-3 in front at the interval, with the division's bottom side on course for only their second win of the campaign.
Matters looked ominous for Garryowen when 'Rock hooker Cian Culleton grabbed a try for the visitors which Keogh converted after 44 minutes.
That score served as a wake-up call for Garryowen and four minutes later experienced flanker Conor Hartigan grabbed a try which Cusack converted.
That great campaigner of many battles, Paul Neville, finished off Garryowen's second try after 66 minutes and the icing on the cake came with a late penalty from Fergal Lawlor.
Referee: Brian MacNeice (IRFU)