Uranium (U) toxicity patterns for fish have been mainly determined under laboratory‐controlled waterborne exposure conditions. Because fish can take up metals from water and diet under in situ exposure conditions, a waterborne U exposure experiment (20 μg L−1, 20 d) was conducted in the laboratory to investigate transfer efficiency and target organ distribution in zebrafish Danio rerio compared with combined waterborne exposure (20 μg L−1) and diet‐borne exposure (10.7 μg g−1). 233Uranium was used as a specific U isotope tracer for diet‐borne exposure. Bioaccumulation was examined in the gills, liver, kidneys, intestine, and gonads of D. rerio. Concentrations in the organs after waterborne exposure were approximately 500 ng g−1 fresh weight, except in the intestine (> 10 μg g−1 fresh wt) and the kidneys (200 ng g−1 fresh wt). No significant difference was observed between waterborne and diet‐borne conditions. Trophic U transfer in organs was found but at a low level (< 10 ng g−1 fresh wt). Surprisingly, the intestine appeared to be the main target organ after both tested exposure modalities. The gonads (57% at 20 d) and the liver (41% at 20 d) showed the highest accumulated relative U burdens.