City had started brightly with Thomspson hitting the bar inside the opening 10 mins and after Ledley's goal Thommo was denied by some excellent defending from Darren O'Dea
The first half delivered a very competent performance from the Bluebirds.
Celtic made changes as they looked to get back into the game in the second half and not even putting on their biggest name striker, Jan Vennegoor of Hesselink, was enough as City held firm. City just used one sub when Miguel Comminges was replaced by Darcy Blake in the final minutes.
Cardiff finished the tournament with 2 wins from 2 and a nine point haul. Guimaraes were second with 5 points, Celtic and Middlesbrough both earned two points each. Premier league? You're having a laugh.
Well done City, a great couple of games and fitting reward to the fans that travelled to the Algarve.
City's next friendly is against Swindon at the County Ground next Tuesday.
Cardiff City: T Heaton, K McNaughton, R Johnson, R Johnson, T Capaldi, M Comminges (D Blake 90), S McPhail (capt), G Rae, J Ledley, S Thompson, R McCormack. Subs: P Enckelman, D Purse, P Whittingham, P Parry, M Kennedy, D Dennehy, R Scimeca, D Blake, J Brown.
Celtic: M Brown, A Hinkel (S McManus 64), P Caddis, B Balde, D O'Dea, S Brown, P Hartley (G Caldwell 67), B Robinson, M Donati, G Samaras (S McDonald 67), P McGowan (J Vennegoor 64). Subs: A Boruk