McKellar studied forestry at the University of Aberdeen, after graduation working for the Scottish Forestry Commission. He later trained at the Royal College of Music as an opera singer. He did not enjoy his time with the Carl Rosa Opera Company and left them to pursue a career singing traditional Scottish songs and other works. From 1959 to 1977 he frequently toured the United States and Canada with other Scottish entertainers such as Helen McArthur, often appearing in small local venues. From 1957 he starred each year in innovative pantomimes by Howard & Wyndham Ltd notably at their Alhambra Theatre Glasgow. In 1958/59 he played Jacob Bray in a successful revival of 'Old Chelsea' by Richard Tauber, along with Vanessa Lee and Peter Graves, which opened in Glasgow and then toured. For a decade from 1960 he starred as Jamie in the new pantomimes devised around him, starting with A Wish For Jamie, followed by A Love For Jamie, which ran at the Alhambra in each of five years, accompanied by Rikki Fulton, and moved after to Edinburgh, Aberdeen and Newcastle. He described these years as the most fulfilling of his stage life outside his international recording career. McKellar toured New Zealand in 1964. On many occasions in the 1960s and 1970s he appeared on the BBC TelevisionHogmanay celebration programme, alongside Jimmy Shand, Andy Stewart and Moira Anderson. He also made numerous appearances on the popular White Heather Club television series, hosted by Andy Stewart. His last Hogmanay Show appearance was on STV in 1991. In 1965, the BBC selected McKellar to represent the UK in the Eurovision Song Contest in Luxembourg. He sang five titles from which viewers selected "A Man Without Love" as the 1966 entry. According to author and historian John Kennedy O'Connor's The Eurovision Song Contest – The Official History, the Scottish tenor – who had changed into a kilt at the last moment – drew gasps from the audience when he appeared on stage. The song was placed ninth of the eighteen entries, making it the least successful UK placing in the contest until 1978. McKellar received scores from only two countries. The Irish jury gave the UK song top marks, one of only two occasions the Irish have done so in Eurovision history. "A Man Without Love" peaked at #30 in the UK Singles Chart in March 1966. His albums The World of Kenneth McKellar, and Eco Di Napoli, had a total of ten weeks presence in the UK Albums Chart. He recorded an album in Afrikaans, entitled Kuier By Ons, which was released just before his tour of South Africa in October 1970. On 31 December 1973, the first Scottish commercial radio station Radio Clyde began broadcasting to Glasgow. The first record they played was "Song of the Clyde" sung by Kenneth McKellar. The same recording featured over the opening titles of the 1963 film Billy Liar. McKellar lived in Lenzie, Glasgow in the house called "Machrie Mhor". Outside music, McKellar wrote a sketch which was performed by the Monty Python team at The Secret Policeman's Ball. This was the only time that a sketch written by a non-member was performed by them. McKellar made the majority of his recordings on the Decca Records label. He also recorded several classical works, including Handel's Messiah alongside Joan Sutherland in a performance conducted by Sir Adrian Boult. After he left Decca in the 1970s he then recorded from 1983–1996 for Lismor records, recording several albums for them before retiring in the late 1990s. McKellar also recorded the musical Kismet with Robert Merrill. He was also notable for his recordings of Gaelic songs in translation such as the Songs of the Hebrides arrangements by Marjory Kennedy-Fraser.
