Endeavour is a prequel to the long-running Inspector Morse series, forming the third instalment of the Morse franchise after Inspector Morse (1987–2000) and its spin-off Lewis (2006–2015).

The series traces the early career of Endeavour Morse after he left Lonsdale College at Oxford University without finishing his degree, served briefly in the Royal Corps of Signals as a cipher clerk, and then joined the Carshall-Newtown Police.

In the closing moments of the pilot, as Thursday asks Morse where he sees himself in 20 years, Morse looks in the rear-view mirror and briefly sees the reflection of John Thaw, the original Inspector Morse actor, while the original series' theme music begins to play; this effect is repeated at the close of the final episode of series 9.

Abigail Thaw, daughter of original Morse actor John Thaw, appears in the series as the editor of the Oxford Mail; in one scene she pauses and asks Morse if she has met him before, suggesting it may have been 'in another life'.

The fourth series, marking the 30th anniversary of Morse on television, features cameos by several actors from the original Inspector Morse series playing early versions of their characters.

One of the last lines in series 8's finale, 'Terminus' — 'It's beginning to thaw' — is considered a subtle nod to John Thaw, the actor who originated the role of Inspector Morse.

In the final episode of series 9, Fred Thursday suffers dizziness and partially collapses while walking with Morse through the quadrangle of Lonsdale College (filmed at the real Exeter College), with shaky camera work mimicking the fatal heart attack Morse suffers on the same spot in the original series' finale, set in 2000.

In the closing sequence of the series finale, Endeavour drives his black Jaguar Mark 1 past a red Jaguar Mark 2 — the iconic car driven by Inspector Morse in the original 1980s series — and a pair of eyes appear in the rear-view mirror as a final nod to John Thaw's character.

The series 3 episode 'Prey' is set at Crevecoeur Hall, the same fictional location used in the Lewis episode 'The Dead of Winter', while actor Jerome Hogg appears in the series 3 episode 'Coda' having previously appeared in the original Morse episode 'Greeks Bearing Gifts'.

A line of dialogue in the second episode of Endeavour, 'Girl' — where Thursday tells Morse 'I'm a good detective. And a poor policeman. No-one can teach you the first' — directly echoes a line from the Inspector Morse episode 'Second Time Around', in which DCI Patrick Dawson calls Morse 'a poor policeman, and a very good detective'.

The pilot episode received upwards of 6.5 million viewers in the UK, leading Guardian writer Mark Sweeny to state that commissioning a full series should be an easy decision.

Critics were generally favourable toward the series, though some noted that its plots were occasionally unsatisfyingly convoluted or concluded in a 'rushed, melodramatic and fairly preposterous' manner.

The original UK DVD release of the pilot ran 89 minutes and, according to Amazon.co.uk reviewers, was missing scenes that had aired on ITV; a complete 98-minute edition was released shortly afterward on 26 January 2012.