The Cypriot broadcaster Cyprus Broadcasting Corporation (CyBC) returned to the Eurovision Song Contest after a one-year absence following their withdrawal in 2014 due to financial and budget restrictions, and organised the national final Eurovision Song Project in order to select the Cypriot entry for the 2015 contest in Vienna, Austria.

Performing during the show in position 15, "One Thing I Should Have Done" was announced among the top 10 entries of the second semi-final and therefore qualified to compete in the final on 23 May.

Cyprus' least successful result was in the 1986 contest when it placed last with the song "Tora zo" by Elpida, receiving only four points in total.

In October 2013, CyBC announced their withdrawal from the 2014 contest citing public opinion regarding the 2012–2013 Cypriot financial crisis and budget restrictions as factors that influenced this decision.

During the first Eurochallenge, the 20 artists that progressed from the auditions were required to make a stage performance of their songs in full without backing dancers and 10 entries were eliminated.

The panel consisted of four permanent members that were joined by varying guest international judges during the Eurochallenges and the final.

The permanent judges were:[14][21] Artists and composers were able to submit their entries to the broadcaster between 14 July 2014 and 5 September 2014 through an online submission form.

[24][25] The 60 selected entries were announced on 20 October 2014, and among the competing artists was 2008 Cypriot Junior Eurovision entrant Charis Savva.

[35] The two guest international judges for the Eurochallenges were Christer Björkman (Head of Delegation for Sweden at Eurovision and supervisor of Melodifestivalen) and Dimitris Kontopoulos (Greek producer).

The six remaining entries competed and the winner, "One Thing I Should Have Done" performed by Giannis Karagiannis, was selected by a 50/50 combination of votes from the judging panel and a public televote.

[36] The two guest international judges for the final were Bruno Berberes (French television director) and Nicola Caligiore (Head of Delegation for Italy at Eurovision).

[27] John Karayiannis made several appearances across Europe to specifically promote "One Thing I Should Have Done" as the Cypriot Eurovision entry.

On 18 April, Karayiannis performed during the Eurovision in Concert event which was held at the Melkweg venue in Amsterdam, Netherlands and hosted by Cornald Maas and Edsilia Rombley.

[40] According to Eurovision rules, all nations with the exceptions of the host country and the "Big Five", consisting of France, Germany, Italy, Spain and the United Kingdom, were required to qualify from one of two semi-finals in order to compete for the final; the top 10 countries from each semi-final progress to the final.

[42] The European Broadcasting Union (EBU) split up the competing countries into five different pots based on voting patterns from previous 10 years.

Around two minutes into the song, the background exploded into flame-like bursts of light on key moments in the lyrics, especially on the 'I should' line.

The jury consisted of five music industry professionals who were citizens of the country they represent, with their names published before the contest to ensure transparency.

This jury was asked to judge each contestant based on: vocal capacity; the stage performance; the song's composition and originality; and the overall impression by the act.