Gutierrez was suing Newcastle, owned by billionaire Mike Ashley, after alleging that he was frozen out of the first-term picture having been diagnosed with testicular cancer in October 2013, a claim which the north east club denied.
Newcastle argued that Gutierrez simply did not feature in their future plans, although the tribunal found that the club made it impossible for the winger to trigger a lucrative appearance-based contract extension worth up to £2m.
“We concluded that the reason why the respondent managed the claimant’s selection was because they no longer wanted him at the club because of his cancer,” concluded the tribunal panel in a 64-page document.
It added that the club “made a very quick decision” after Gutierrez’s return following treatment at the end of 2013, “that they no longer wanted him, because of his cancer.”
The issue of compensation will be addressed at a remedy hearing, which will be held in due course.
A further claim that the club failed to make reasonable adjustments for Gutierrez succeeded, although two others of unfavourable treatment and harassment failed.
Gutierrez spent seven seasons at St James’ Park, scoring 10 goals in 177 appearances, after joining from Real Mallorca in 2008. The 32-year-old currently plays for Spanish side Real Sociedad.