There is an interest in replacing soybean meal with locally produced ingredients in livestock feeds. Narbon vetch is resistant to unfavorable climatic and soil conditions, common pests, and has a favorable nutritional profile. The effect of substitution of soybean meal with 0% (V0), 5% (V5), 10% (V10), and 20% (V20) inclusion of Narbon vetch on growth curve parameters, daily body weight gain (DBWG), daily feed intake (DFI), feed conversion efficiency (FCE), and residual feed intake (RFI) was investigated in 47 Duroc × Iberian barrows in 16 periods (a total of 125 d). DFI and DBWG were reduced (p < 0.05) up to four weeks after introduction of the novel feed in V20 and V10. Small, mostly nonsignificant differences existed between treatments in FCE and RFI. However, because of accumulative small differences in feed efficiency between the four diets, pigs in V0 reached the highest BW, and pigs in V20 reached the lowest BW on a similar feed intake. Economic implications of Narbon vetch inclusion depend on the extra amount of feed required and associated feed costs, and on the costs of additional days on-farm required to reach a given slaughter weight.