The hosts raced into a 17-0 lead courtesy of tries from Garyn Lucas and James Loxton with Dean Gunter adding two conversions and a penalty.
However, the Ospreys struck back to make it 17-9 at the interval, with leading points scorer Matthew Jarvis kicking three well struck penalties.
A try from Richard Randall and nine more points from the boot of Jarvis threatened to spoil the Blues’ party, but Dean Gunter won the day and finished the evening with 16 points.
Blues community and coach development manager Richard Hodges said; “The boys played well early on, but did their best to throw it away in a very tight game.
“However, they stuck in there and gained a valuable win against a very good Ospreys’ side.”
