He became first choice goalkeeper for Kaunas with his impressive displays against Scottish side, Rangers and Danish champions AaB Aalborg which helped earn him a move to Hearts.
[4] He maintained his place in the team until the Edinburgh Derby on 19 October 2008 when he suffered a head injury in a clash with Hibs striker Colin Nish and had to be replaced by János Balogh at half-time.
On 2 October 2010 Kello turned in a heroic performance against Rangers only for Hearts to succumb to a stoppage time goal from Steven Naismith in a 2–1 loss at Tynecastle.
[12] His impressive form continued as he saved a stoppage time penalty from David Goodwillie to preserve a 2–1 win against Dundee United as Hearts extended their lead in third place in the league.
[15] Following the dismissal of Jefferies as manager at the start of the 2011–12 season and appointment of Paulo Sérgio Kello continued as first-choice goalkeeper.
He missed the Scottish Cup tie against St Johnstone the following weekend, it was originally reported his absence was due to a back injury.
[18] With interest from Aston Villa and other English clubs to sign a pre-contract agreement,[19] on 5 April 2012 Kello agreed to an early termination to his Hearts contract.
[23] He then joined Wolverhampton Wanderers on trial[24] and played the full match in a pre-season friendly against AFC Telford United in a 2–0 victory[25] but again no permanent deal was agreed.
With Romanian international Silviu Lung Jr. firmly established as first-choice goalkeeper Kello made only two appearances before being released by the club in December.
On 28 March 2013 Kello signed for English Championship club Wolverhampton Wanderers in a short-term deal until the end of the 2012–13 season as cover for their injured goalkeepers Wayne Hennessey and Carl Ikeme.
Kello's impressive form for Hearts in early 2011 saw him called up to the Slovakia squad and he made his international debut on 9 February 2011, as a substitute against Luxembourg in a 2–1 defeat.