The effect of BaCeO (BCO) dopant concentration on magnetically obtained irreversibility field B and upper critical field B 2 is investigated in YBaCuO+x (YBCO) thin films prepared by pulsed laser deposition on SrTiO (001) substrates. The unchanged values of B and B2 are connected to the structural properties where BCO has been observed to form non-elongated and randomly distributed particles within the whole concentration range of 0-10 wt.%. This indicates a different type of flux pinning mechanism for BCO-doped YBCO than for the widely studied BaZrOoped YBCO where increased B and B2 values were observed. © Published under licence by IOP Publishing Ltd.