Considering the expanding use of reclaimed asphalt pavement (RAP) in line with the development of sustainable pavements, the presence of aged binder in RAP can lead to increased stiffness, reduced moisture resistance, and a decline in the capacity to heal micro‑cracks; therefore, finding a method to preserve the performance of RAP‑containing mixtures while enhancing self‑healing capabilities is an important research need. The innovation of this study is the simultaneous examination of the effect of RAP and nano sodium alginate (NSA) and the integrated evaluation of the mechanical performance, thermal stability, moisture sensitivity, and resistance to permanent deformation of asphalt mixtures. For this purpose, asphalt mixtures with 0, 50, and 100% RAP and 6% NSA were prepared, and their performance was evaluated using the Marshall stability, thermogravimetric analysis (TGA), dynamic creep, and indirect tensile strength (ITS) tests. Results showed that increasing RAP improved Marshall stability under dry conditions but reduced it under wet conditions, whereas adding NSA compensated for this weakness by strengthening the binder–aggregate adhesion. TGA results indicated enhanced thermal stability and greater resistance to thermal degradation in NSA‑modified samples. In the dynamic creep test, RAP0 control sample withstood only about 538 loading cycles, while RAP100+NSA sample remained stable for approximately 10016 cycles without entering the failure zone, showing a substantial improvement in resistance to permanent deformation. ITS results showed that increasing RAP reduced the tensile strength ratio from about 0.915 in the control sample to about 0.786 in the 100% RAP mixture, whereas NSA increased this value to about 0.971 for RAP0 and about 0.845 for RAP100. Overall, combining RAP and NSA significantly enhances key performance indicators, enables greater use of recycled materials, and supports sustainable pavements aligned with a circular economy.