Melodifestivalen 1978 was the selection for the 18th song to represent Sweden at the Eurovision Song Contest. It was the 17th time that this system of picking a song had been used. 58 songs were submitted to SVT for the competition. The final was broadcast on TV1 but was not broadcast on radio. The songs were not performed live, instead the performances were recorded the afternoon before, and inter-mingled with live pieces from the venue. There was a tie in the voting, and each regional jury was asked to award one point to their favourite song of Det blir alltid värre framåt natten and Miss Decibel. The former won by eight votes to three.

Melodifestivalen 1978 sändes den 11 februari 1978 i TV 1 20.00 - 22.05 från Cirkus i Stockholm. Melodin Det blir alltid värre framåt natten, framförd av Björn Skifs, vann och fick representera Sverige i Eurovision Song Contest 1978.

Melodifestivalen 1978 was de zeventiende editie van de liedjeswedstrijd die de Zweedse deelnemer voor het Eurovisie Songfestival oplevert.

El Melodifestivalen 1978 tuvo lugar el 11 de febrero de 1978, y no se retransmitió en directo. El presentador fue Ulf Elfving, y la dirección de la orquesta corrió a cargo de Anders Berglund.