Porcine immature oocytes derived from small follicle (SF, ≤3 mm in diameter) are able to resume meiosis, but few oocytes are capable to progress to the metaphase 2 stage. To improve capacitation of oocytes derived from SF and inhibit spontaneous maturation, a pre-in vitro maturation (IVM) system was applied to in vitro culturing of cumulus–oocyte complexes (COC). Pituitary adenylate cyclase-activating peptides (PACAP), increasing cellular cyclic adenosine 3′5′-monophosphate, have pleiotropous actions and multiple functions throughout the body as a neuropeptide. Recently, studies have described the role PACAP play in fertility and reproduction, including follicular development, antiapoptotic effects, and implantation. The purpose of this study is to improve the developmental competence of oocytes derived from SF by exogenous addition of PACAP on pre-IVM. In the conventional IVM group, COC obtained from follicles ≤3 mm in diameter (SF group) and 3 to 6 mm in diameter (medium follicles; MF group) were subjected to IVM for 42 h. In the pre-IVM group, COC obtained from SF were matured with nontreatment [pre-SF(-)PACAP group] and 1μm PACAP [pre-SF(+)PACAP group] for 18 h pre-IVM and were immediately subjected to IVM for 42 h. We examined nuclear stage assessment, intracellular reduced glutathione and reactive oxygen species levels, and embryo developmental competence by parthenogenesis and IVF. After IVM, the result of the nuclear stage assessment of groups showed that the pre-SF(+)PACAP group had the highest metaphase 2 rate in the groups (P < 0.05). Reduced glutathione levels in MF and pre-SF(+)PACAP groups showed significantly higher levels than that of the other groups (P < 0.05). After parthenogenesis, the cleavage rates were significantly (P < 0.05) higher than the others in pre-SF(+)PACAP group. In the IVF experiment, the embryo cleavage rate was significantly higher in that of MF and pre-SF(+)PACAP groups compared with that of SF and pre-SF(-)PACAP groups (P < 0.05). Moreover, no significant differences were found in the cleavage rate between MF and pre-SF(+)PACAP groups. In all groups derived from SF, the pre-SF(+)PACAP group rate of blastocyst formation and total cell number of blastocysts was significantly higher than that of the other groups (P < 0.05). These results indicated that pre-IVM system using PACAP is able to improve meiotic maturation and developmental competence although the oocytes were derived from SF.