Nelson's version, issued as the B-side of his No. 1 hit "Travelin' Man", (Imperial 5741), reached No. 9 on the Billboard music charts on May 28, 1961. In the United Kingdom, where it was released as an A-side (with "Travelin' Man" as the B-side), it reached No. 2. It was also a hit in much of Europe, particularly Norway, where it spent 14 weeks at No. 1. In New Zealand, the song reached No. 4.

A 1991 reissue following the song's use in a TV advert gave the song a second chart run, peaking at No. 45 in the UK Singles Chart.

The song features an influential guitar solo by James Burton, often cited by later guitarists such as Brian May. Piano was by Ray Johnson, who had succeeded Gene Garf as Nelson's regular session pianist in November 1959. other musicians on the record included Joe Osborne on bass and Ritchie Frost on drums.

The song appears on Nelson's sixth album Rick Is 21.

Hello Mary Lou was not strictly an original composition. Pitney reworked a version of an earlier song 'Merry, Merry Lou', recorded by a band called The Sparks in 1957, which was covered later that year by Bill Haley & His Comets, as 'Mary Mary Lou'. The composer of the track was Cayet Mangiaracina, band member of The Sparks, who would later become ordained as a Catholic priest. When Hello Mary Lou was released, the recording company Decca sued for plagiarism of this song and won. Furthermore, Mangiaracina was awarded writer co-credits for Hello Mary Lou as composer of the original song.

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