Gibbs and Hamilton City Hawks' Sarah Biss sat shoulder-to-shoulder before Gibbs, kicked clear at the 6km mark to win easily.
Lett's solitary sojourn last night got the blame for his slower time.
"I usually start a bit slower and finish quick but tonight seemed to be the opposite for some reason - running by yourself does make a bit of a difference. "My time at 5km [15:06] was the same but it's that bit harder on the track and having a couple of guys with you to share laps, meaning you can hide for a lap, certainly seems to make it easier.
"It's probably more of a mental effort required than anything because going solo you have to concentrate a lot more and focus on your own effort, but I went out at the pace I wanted to go and and no one came with me."
Lett was chasing a sub-30min time but his lack of back-end pace meant he faded over the last 4km. "It didn't quite happen but last year I had Jono [Jackson] and Alex around for company."
Jackson (Auckland City Athletics) was in the silver medal position for half the journey, hitting 5km in 15:22, closely followed by Luke Hurring (University of Canterbury) but gave up the spot soon after, with Hurring second home in 30:57.25 and Jackson holding on for third (31:07.59). Athletics Tauranga's Angus Bell ran well for fifth, with Alex Gorrie (32:03.31) taking the M20 title.
Lett, who won the 10km, half marathon and road titles last year, has his sights set on the 5km track title US-based Nick Willis won last year in Dunedin.
RESULTS 10,000m New Zealand Champs (Tauranga Domain)
M20: Alex Gorrie (University Canterbury) 32:03.31, Malcolm Hodge (University Canterbury) 34:28.46, Talor Gilmer (Wellington Harriers) 34:59.83.
Senior women: Sally Gibbs (Athletics Tauranga) 34:45.21, Sarah Biss (Hamilton City Hawks) 35:09.79, Kellie Palmer (University Canterbury) 35:39.21.
Senior men: Stephen Lett (Takapuna) 30:36.35, Luke Hurring (University Canterbury) 30:57.25, Jonathan Jackson (Auckland City Athletics) 31:07.59, Cory Whiting (Hamilton City Hawks) 31:40.92, Angus Bell (Athletics Tauranga) 32:08.94.