Linear and crosslinked polyimide aerogels have been synthesized by means of a simple and eco-friendly process. Water-soluble poly(amic acid), PAA, solution was produced and thermal imidization was employed. Furthermore, freeze drying was used. In the present work, the influence of the solid content of the PAA solution and the crosslinking addition on the properties of the resulted aerogels were evaluated. An increase in solid content resulted in denser structures. Thermogravimetric analysis demonstrated thermal stability of polyimide aerogels up to 550°C. Moreover, the crosslinking addition resulted in mechanical properties improvements. In addition, the obtained polyimide aerogels retained an oil amount of 14 times higher than its dry weight. Besides, polyimide aerogels showed very good values of sound absorption coefficient (maximum value of 0.91) and low thermal conductivities (0.038–0.045W/mK). Summarizing, PI aerogels presented very good thermal and acoustic insulation properties, excellent thermal stability and good oil sorption capability.