In another close game Kerry ended on the right side of a 3-10 to 1-11 scoreline to give O'Sullivan a first Munster title in the grade.

Unlike during Munster Kerry ran out comfortable winners on a 1-14 to 0-09 point scoreline, with O'Sullivan once again at full back.

O'Sullivan was back in the no 3 jersey for the start of the 1999 championship as Kerry ran out easy winners in the first round on a 1-22 to 1-04 scoreline against Waterford.

Despite being closer than the first two games O'Sullivan's side still ran out comfortable 1-10 to 0-07 winners, giving O Sullivan his second Munster title.

However at the final whistle Kerry found themselves at the wrong end of a 1-12 to 0-09 scoreline in one of the biggest shocks in the history of the championship.

He played full back in the Munster semi final as Kerry were held to an 0-11 each draw by Cork.

[citation needed] Tom O'Sullivan made his debut for the Kerry seniors against Cork in the 1999/2000 National Football League.

In the replay, again like the semi-final another close game played out with Kerry winning on a 0-17 to 1-10 scoreline, giving O'Sullivan his first All Ireland medal.

This set up a semi final with Limerick, in a game where Kerry again ran out comfortable 1-15 to 0-10 winners.

In the end of a huge scoring game Kerry were winners on a 0-19 to 1-13 scoreline, giving O'Sullivan a second Munster title in a row.

2001 was the first year of the qualifier series meaning for the first time there was a quarter final stage, where Kerry met Dublin.

A week later the two teams were back in Thurles and after another exciting game Kerry ran out winners on a 2-12 to 1-12 scoreline.

On a wet ran in Killarney a low scoring 0-08 a piece scoreline, meant the sides would have to meet again.

The win meant Kerry were back in Croke Park for a Q/F tie with All Ireland champions Galway.

After losing out in Munster Kerry made no mistake second time around and routed the Rebels on a 3-19 to 2-07 scoreline.

This set up a Munster final with Limerick, who had pulled off a shocked result with a 10 pint win over Cork in the semi-final.

O'Sullivan finished the year playing at Left corner back in all 4 of Kerrys championship games.

After some disappointing losses in Croke Park over the previous three seasons, Jack O'Connor took over as manager replacing Páidí Ó Sé.

A last-gasp catch from a 45 from Darragh O Se meant the sides finished level on a 1-10 each scoreline, meaning they would have to face off once again a week later in Killarney.

In somewhat of a surprise Kerry ran out easy winners on a 1-20 to 2-09 scoreline, giving O'Sullivan a second All Ireland medal.

He ended the year with a clean sweep of National League, Munster and All Ireland medals along with an All Star.

Kerry kicked off the defense of their All Ireland title with a 2-22 to 0-13 Tipperary in Thurles, with O'Sullivan in his now established Corner Back slot.

In a much closer game then 2004 Kerry ran out winners on a 2-15 to 0-18 scoreline in what was to be a tough afternoon for O Sullivan where he was replaced by Eamonn Fitzmaurice.

[3] However, he struggled at times in the Munster final against Michael Cussen of Cork and in the All-Ireland quarter-final against Vincent Corey of Monaghan.