The new manager and his assistant looked comfortable in each other’s company as they put the squad through their paces at the training ground in Gannon Park, Malahide, Co Dublin.
But there were also glimpses of steely determination as the pair plotted their strategy and assessed their players.
Keane arrived 90 minutes before training was due to begin at 11am.
Keane went straight on to the training pitch to ensure everything was in place for the start of the morning session and then inspected the nearby gym facilities.
However, the former Ireland and Manchester United skipper, who was wearing full training kit, had time to sign autographs and pose for photographs with fans who had turned out to witness the birth of the new regime.
But he was back on the pitch long before the first wave of players, headed by current skipper Robbie Keane, arrived at 10.45am.
The smiling LA Galaxy striker expressed mock surprise at the size of the media pack which had assembled well in advance of the scheduled start amid a relaxed atmosphere.
O'Neill and the remainder of the squad arrived within minutes on the team coach and he and Keane looked on as the players warmed up, with keepers David Forde, Keiren Westwood and Rob Elliot working apart with new goalkeeping coach Seamus McDonagh.
The management duo looked on from the sidelines, with Keane at one point dispatching a stray ball into a goal standing at the side of the pitch.
But the real work began once the cameras had been switched off and journalists asked to leave after their allotted time, with a new era in Irish football well and truly under way.
O'Neill, who was formally unveiled at a press conference in Dublin on Saturday afternoon, was due to speak to the media once again this afternoon with Keane scheduled to hold his first press conference 24 hours later.
Last night, O'Neill and Keane met the players they have inherited last night ahead of the training session today. Earlier yesterday, they toured the Aviva Stadium, with the Corkman having a look at the facilities, which have changed dramatically since he played at the old Lansdowne Road.
Anthony Pilkington is the only fresh injury concern for the double header with Latvia and Poland after he sustained a dead leg in Norwich's Premier League clash with West Ham on Saturday. He will stay with his employers for treatment and may link up with the Ireland squad later in the week.
Robbie Keane expects to figure but appears to have ruled out a loan move to the Premier League this winter after stressing that he needs recuperation time to shake off a series of injury problems that have dogged him this year. LA Galaxy's season is over after their dreams of retaining the MLS Championship were ended by Real Salt Lake last Thursday.