The Aussie star was all over the field as Everton got their new year off to a flying start.
Perhaps it was the lucky win at Sunderland or being led out by captain Duncan Ferguson, either way the Blues looked like a new team and took control of the game.
The Goodison faithful erupted when Kevin Kilbane was brought down in the area by Dennis Rommedahl. They cheered as if they had already scored when referee Uriah Rennie pointed to the spot.
But when James Beattie calmly stepped up, keeper Thomas Myhre read it well.
He dived to the left and managed to block the kick, but Beattie reacted quickly to put the rebound away for the opening goal.
Everton showed rejuvenated confidence as they began to produce some clever build-up play.
The Blues hero in the win against Sunderland, Cahill, ignited the midfield as he danced through three white shirts.
And even as he was hacked in the area the Aussie man still managed to get the ball to Beattie and the referee played advantage. Beattie found Leon Osman in the box but his effort was stopped.
But as Everton put the pedal to the metal in attack they were caught napping in defence.
A wayward header bounced perfectly for Matt Holland on the edge of the area and without looking up he unleashed a scorching right-foot volley which Nigel Martyn had no chance of reaching.
However, Everton's blue tide couldn't be stopped and they continued to pile the pressure on the Addicks. Kilbane played a fine cross into Ferguson which he met with an acrobatic overhead kick, but the effort was snaffled.
And it was Kilbane again who powered his way into the box for a thunderous header which was only saved by the far post.
But Myhre was beaten again as the Blues stole a physiological advantage and the lead on the stroke of half-time. Captain Ferguson won a free-kick 40 yards out and Mikel Arteta took it quickly.
His pass found Cahill storming in at the near post and his header bounced off the underside of the crossbar and into the net to excite the Goodison Park crowd.
Alan Curbishley must have read his team the riot act because they came out after the break with renewed energy and hunger for the ball.
The play went end to end, as Charlton hustled for an equaliser and left themselves open on the counter-attack.
Everton gave themselves a comfortable two-goal buffer on 58 minutes and it was almost like an action replay of their second goal.
Arteta stepped up to take a free-kick just outside the box and floated the ball towards goal while Cahill managed to out-muscle two defenders and head the ball home.
The Aussie international should have had a hat-trick with a tap-in during a goalmouth scramble, but had it disallowed by referee Rennie for a Ferguson foul.
Cahill nearly scored again from 20 yards with a last-gasp strike from a deft lay-off by Marcus Bent, but this time he was denied by the post.