Pure and (Co, Al) co-doped (Co=1, 3, 5 mol %, and Al = 5 mol % as constant) SnO2 nanoparticles were synthesized in aqueous solution by the chemical co-precipitation method using polyethylene glycol (PEG) as a stabilizer. The effects of structural and photoluminescence of (Co, Al) co-doped SnO2 nanoparticles are investigated. The XRD pattern reveals that the samples are in a single phase rutile type tetragonal crystalline structure of SnO2. The peak positions with Co concentration are slightly shifted to lower 2θ values and size of particles from XRD calculations are in between 20–30 nm. The Raman studies of the samples reveal that the Raman peaks are shifted towards lower wave numbers, when compared to those of pure SnO2 at 150 cm−1, 303 cm−1, 476 cm−1, 630 cm−1, and 765 cm−1 respectively. Photoluminescence studies show that pure SnO2 has an emission peak at 444 nm and (Co, Al) co-doped samples show emission peaks at 417 nm, 433 nm and 485 nm with exciting wave length 320 nm. The PL intensity increases and broadening of peaks for co-doped samples with increase of Co concentration indicates the decrease of size of the crystallinity. The UV absorption spectrum exhibits absorption at 310 nm, and is in agreement with the emission spectra.