Eduardo Rivadavia in his review for AllMusic calls Under Lock and Key "quite possibly Dokken's most 'complete' album, with a little something for every type of fan", like "fist-pumping headbangers", extraordinary "bittersweet mid-paced rockers" ("Unchain the Night" and "The Hunter") and "saccharine ballads". Rivadavia recommends the album as the best introduction to new listeners of Dokken, but notes that heavy metal purists would likely prefer the band's 1984 album Tooth and Nail. Canadian journalist Martin Popoff considers the album "too weighted towards Def Leppard's fat-and-open formula rock", resulting "a bit subdued and predictable" in comparison with its predecessor. The band's glamorous look, the media exposure and George Lynch's "attempt to define the L.A. sound in his own image" do not save Under Lock and Key from sounding "like the work of a band just fed".
The music videos produced for the singles from the three Dokken's albums were featured on a longform videocassette release, Unchain the Night, by Elektra/Asylum Records through Elektra Entertainment. That video debuted on Billboard's Top Music Video—Longform chart at No. 11 in January 1987, peaking at No. 5 that May. The video collection was certified Gold in April 1987, and Platinum the following April. In 2007 the collection was re-released in DVD by Rhino Home Video through Warner Music Vision, debuting on the Billboard Comprehensive Music Videos chart at No. 27.