Level populations and line intensity ratios are calculated in a 35 level model of Fe XV using most recently available atomic data and incorporating the effects of self-absorption through escape probability factors for slab and cylindrical sources. The computed optically thin spectrum is found to agree very well with solar active region observations, confirming the correctness of the atomic data. Under optically thick conditions, a different situation is found compared to the Fe XVII spectrum; all Fe XV subordinate lines and their intensity ratios are unaffected. At the same time the 284.16 Å resonance line exhibits the counterintuitive effect of initial intensity increase with column density even more strongly than do Fe XVII resonance lines. A preliminary comparison is made with the available observations, which are found to be consistent with the present predictions.