With a 13-11 lead at the interval, Glen Dickson stepped up to rack up his third penalty of the night in the 43rd minute.
Tyler Bleyendaal made sure his team were never far behind and three minutes later reestablished the two point deficit before giving his side the lead for the first time at 17-16 in the 51st minute.
Canterbury have improved markedly all season demonstrating a calmed composure with a sixth sense in understanding that reward would follow the hard toil.
After having to defend a number of Otago's attacking raids into their half, their defensive work eventually frustrated their opponents into running across field and in to making poor kicking plays and Tom Taylor benefited.
Buxton Popoali'i provided plenty of excitement with his jinking side-steps and runs but a chip-kick over the defence was regathered by fullback Taylor who went through a gap before gassing away over 60 metres.
Bleyendaal missed another sitter and with just a six point margin separating the teams it was always going to be a cause for concern with 20 minutes remaining.
Both teams had their opportunities to execute a check-mate move with Popoali'i for Otago and Crotty from Canterbury looking most likely to spark a game-changing play.
The former would instigate the decisive play, only it would end up in the hands of the opposition.
Charging back into the opposition half Popoali'i passed back infield only for Robbie Fruean to pick off the pass and sprint 65 metres to kill off Otago' hopes with six minutes to go.
In the closing stages of the match, Canterbury went in search of a fourth try to cement a home final while Otago looked to pay back the home crowd's enthusiasm with a try.
A try to either side never arose, but Canterbury will nevertheless be satisfied they will challenge for silverware next weekend.
Earlier, Otago were fortunate to go into the break ahead by their 13-11 lead after Bleyendaal missed an easy conversion that would've given his side parity at the break.
The 20 year old first-five scored the first ITM Cup points on the ground with a penalty in the fifth minute of play.
Canterbury's early pressure on the Otago tryline wasn't the five-pointer they wanted but the penalty settled the nerves for his team who needed the win to secure a place in next week's Premiership final.
Otago, cheered on by a healthy 15,000 fans, struck back with a try to winger Ben Smith after centre Ben Atiga made a break on halfway before his offload found Smith who burrowed over. Dickson converted.
A thumping tackle from veteran first-five Tony Brown brought to end a Canterbury attack and earned his side a penalty which Dickson easily nailed over the crossbar to go up 10-3.
Three minutes later the Cantabs crashed over the tryline with Bleyendaal dotting down after great buildup play by Ryan Crotty. However the tryscorer's relatively straight-forward conversion from beside the uprights went astray.
Dickson and Bleyendaal traded penalties to take the teams to the break.
Canterbury 29 (Tyler Bleyendaal, Tom Taylor, Robbie Fruean tries; Bleyendaal 4 pen, con) Otago 16 (Ben Smith try; Glenn Dickson 3 pen, con). Halftime: 11-13.
- HERALD ONLINE
