The highly-rated 28-year-old resigned from the same position at La Liga side Valencia just two weeks ago citing family reasons.
He had been linked with the vacant manager???s job at Rangers before Mark Warburton was named as the new man in charge at Ibrox on June 15.
Now he is poised to take up a role on Tyneside instead and add to what is already an impressive CV given his young age.
Cathro has never played professionally and only played youth football for Scottish lower-league sides Forfar Athletic and Brechin City.
He has, however, built a solid reputation as a coach and became the head of Dundee United???s academy at just 22.
Among the players he mentored was Scotland U21 international Ryan Gauld, who was transferred to Sporting Lisbon from Tannadice a year ago for a fee of around ??3m.
By then, Cathro too had also gone to Portugal having been named as assistant manager at Rio Ave under Nuno Espirito Santo.
He then followed Santo to the Mestalla last summer and helped Valencia to a fourth-place finish with a sequence of results which included wins over Atletico Madrid, Real Madrid and Sevilla.
Cathro has come up against Newcastle before and oversaw a 3-1 friendly win against them with Santo???s Rio Ave team two years ago.
Now he is set to move to the city as part of McClaren???s backroom team before pre-season starts next Wednesday.