During the last years, the high growth of the livestock production sector has caused a high demand of raw material in order to feed the animals. This higher demand has environmental consequences and a more sustainable strategy is required for livestock production. Some agro-industrial by-products such as olive cake may be beneficially used without a decrease in production traits. Here, we studied the effect of three different dietary regimens given to Iberian pigs in growing period (42 kg to 95 kg) on several growth and slaughter traits. A control standard diet group (CD) was compared with two diets based on olive by-products, one incorporating dry olive pulp in the feed (DD), and the other one incorporating olive cake in wet form (WD). This last one consisted of olive cake in a silage presentation offered ad libitum and supplemented with a specific feed given once a day in a restricted regimen as the CD and DD diets. A significantly higher average daily gain during the growing period was observed for WD diet compared with DD diet. However, this was compensated with a higher average daily gain of DD pigs during the fattening period (acorn and grass). Carcass yield was lower in DD than CD and WD pigs, but no significant differences were observed for premium cut yields, which are more important for the Iberian industry. Therefore, the diets based on olive cake does not seem to alter the growth and slaughter traits studied, however, before its implementation in feeds used for the growing period, further studies analyzing their effects on meat quality and production costs should be carried out.