Are gecko's nocturnal?

Yes, geckos are nocturnal but you can still see them awake in the daytime. Example is a leopard gecko, rarely you would see them up in the day.

Although most gecko species are nocturnal, doing their daily activities at night, some species of gecko are diurnal. This means that they are active during the day. These species of geckos are called Phelsuma (day geckos).