Climate change is a concerning phenomenon worldwide. The reduction in greenhouse gas emissions is the core of the mitigation strategies that are effective countermeasures to address a changing climate in the long term. Nevertheless, the need for short-term solutions regarding adaptation to climate change (ACC) has gained growing interest in the scientific community and in European institutions. European and national ACC principles are being integrated in strategies and plans. In Italy, some regions have adopted ACC principles in strategic plans, which influence the whole local planning system and persuade local communities to become more climate-resilient. This study focuses on the mainstreaming of ACC into strategies, plans, programs, and projects (SPPPs) adopted by the following Italian cities: Bologna, Milan, Naples, Rome, Turin, and Venice. We scrutinize the contents of SPPPs with respect to four criteria: (i) references to strategies or plans for ACC; (ii) inclusion of ACC objectives and (iii) measures; and (iv) references to—or the inclusion of—climatic analysis on historical series and/or future projections. We found out that most SPPPs adopted by the cities have considered ACC in a promising way, i.e., all the cities are inclined to promote ACC, despite three of them lacking a municipal ACC strategy or plan and a National Adaptation Plan not being in force.