An Otere Black penalty after the full-time siren secured the Blues' second win of the season, beating the Bulls 23-21 in Pretoria.
In a clash dampened by heavy rain, the Bulls led 11-8 at the break but could not repel a comeback from the away side, who took a 20-14 lead late in the second half.
A try straight after the break from Tom Robinson put the Blues into the lead, which was extended with another five-pointer to fullback Steven Perofeta with 20 minutes to play.
Having been dominated by the Crusaders last week, the Blues' desperation led to ill-discipline and Hoskins Sotutu was sin-binned in the 69th minute.
The Bulls looked like they might record their first win of the season after a try put them in front with 10 minutes to play - but Black's penalty became the deciding factor for the Blues, who were also desperate for a win.
It was a match marred by ill-discipline with four yellow cards. Along with Sotutu, Blues halfback Jonathan Ruru was sent to the sin bin in the first half for slowing the ball down, while the Bulls were reduced to 13 men at one stage with Burger Odendaal and Andries Ferreira given their marching orders for foul play and a dangerous tackle.