From 10 October, 4000 poster sites nationwide will feature the yellow i-mode logo in a two-week teaser campaign to raise awareness.
This will be followed by TV, online, press and outdoor ads, created by Vallance Carruthers Coleman Priest (VCCP).
From 1 October, O2 will be the first UK mobile operator to offer i-mode, which is already a huge success in Japan.
The company has signed up a number of major content partners, including Lastminute.com, Interflora and Egg ahead of the run-up to the Christmas period.
I-mode is effectively mobile internet at the click of a button. It is viewed by O2 as its main weapon to halt customer churn and compete against the 3G offerings of rivals Vodafone and 3.
According to Russ Shaw, marketing director of O2, it will sit at the heart of its new customer focus strategy, which is also being backed by a multimillion-pound marketing investment.
'At the moment, customers are more interested in handsets and tariffs than data. We're not going to change things overnight but with i-mode it will get a lot easier,' he said.