Born in County Kilkenny, Tennyson first played competitive hurling whilst at school in St. Kieran's College.
He arrived on the inter-county scene at the age of seventeen when he first linked up with the Kilkenny minor team, before later lining out with the under-21 and intermediate sides.
As a member of the Leinster inter-provincial team on a number of occasions Tennyson won one Railway Cup medal .At club level he continues to play for Carrickshock.
Having come close to beating the Fermoy-based school at the same stage the previous year, St. Kieran's made no mistake this time and recorded a 1–15 to 1–4 victory, giving Tennyson an All-Ireland medal.
Richie Power gave a masterclass of hurling, including scoring the winning point deep into injury time, to secure a 2–16 to 2–15 victory.
[19] Kilkenny's bid for a third successive All-Ireland title ended in dramatic fashion as a late point from Kerril Wade handed Galway a narrow 1–15 to 1–14 victory.
[20] For the third successive year Tennyson won a Leinster medal following a 2–18 to 2–10 defeat of Dublin before later lining out in the All-Ireland decider against Tipperary.
[21] The replay was another close encounter, however, Paddy Hogan's first half goal helped Kilkenny claw their way to the title following a 1–11 to 0–11 defeat of Tipperary.
On 3 September 2006 Kilkenny faced a Cork team who were presented with the opportunity to become the first side in nearly thirty years to secure three successive All-Ireland championships.
[26] On 2 September 2007 Kilkenny faced defeated Munster finalists and surprise All-Ireland semi-final winners Limerick in the championship decider.
Kilkenny got off to a flying start with Eddie Brennan and Henry Shefflin scoring two goals within the first ten minutes to set the tone.
An injury hampered Tennyson's 2008 championship campaign, however, he collected another set of Leinster and All-Ireland medals as a non-playing substitute.
[28][29][30] Tennyson was back on the starting fifteen in 2009, and collected a second league medal as Kilkenny beat Tipperary by 2–26 to 4–17 with a thrilling extra-time victory.
[32] On 6 September Kilkenny were poised to become the second team ever in the history of hurling to win four successive All-Ireland championships when they faced Tipperary in the decider.
For long periods Tipp looked the likely winners, however, late goals from Henry Shefflin and substitute Martin Comerford finally killed off their efforts to secure a 2–22 to 0–23 victory.
"The Cats" lost talisman Henry Shefflin due to injury, while Tipperary's Lar Corbett ran riot and scored a hat-trick of goals as Larkin's side fell to a 4–17 to 1–18 defeat.
[37] After failing to make any appearances during Kilkenny's successful league campaign in 2013, Tennyson decided to retire from inter-county hurling before the start of the championship.