The win extended their winning streak at home to 36 games, but was hard earned after the Blues led for the first 60 minutes.
Both sides were unbeaten after their first three games of Super Rugby Aotearoa, with the Blues also boasting four straight wins before Covid-19 suspended the original Super Rugby competition.
The Blues drew first blood tonight, just 10 minutes after kick-off, building pressure before Otere Black's wide ball found Mark Telea on the right wing.
Black nailed the conversion, and the visitors held a 7-0 lead until Crusaders playmaker Richie Mo'unga nailed two penalties to narrow the lead to a single point 10 minutes out from halftime.
The Blues had earlier suffered a blow in losing hooker James Parsons to a head injury after 25 minutes, but their well-organised defence held the Crusaders at bay under pressure to take a 7-6 lead into halftime.
The Blues' second try came in the 55th minute from a scrum penalty. It started with Akira Ioane's quick tap, and ended when brother Rieko bulldozed across soon after.
Centre Braydon Ennor charged down Black's attempted conversion, a miss which proved telling five minutes later when Mitchell Drummond latched onto George Bridge's inside pass to dot down for a Crusaders converted try.
Mo'unga's penalty gave the Crusaders the lead for the first time in the match as the hour mark ticked over, a lead extended soon after by another penalty as the home team took a 19-15 lead with 13 minutes remaining.
A sniff was all the Crusaders needed - they upped the pressure, and Mo'unga's kicking game kept the Blues pinned inside their own 22 until the gap inevitably opened and Will Jordan sidestepped his way across.