Objective: The most common cancer in smokers is bladder cancer (BC). Intravesical chemo immunotherapies are used to lower the risk of progression in patients who are at risk. Bacillus Calmette-Guérin immunotherapy is the most effective adjuvant therapy discovered. We aimed to evaluate the levels of arginine, citrulline, ornithine, symmetrically dimethylated arginine (SDMA), N-monomethyl-Larginine. (L-NMMA) or asymmetrically dimethylated arginine (ADMA) in patients with BC, as well as their relationship with methylarginine. Materials and Methods: Blood samples were collected from all patients (n=30) and controls (group 1) prior to transurethral resection of bladder tumour (TURBT) (group 2), 20 days after TURBT (group 3) and at the end of intravesical immunotherapy 74 (group 4). The levels of serum methylated arginine were measured using ABSCIEX API 3200 tandem mass spectrometry system in positive ESI mode. Results: In comparison to group 2, group 1’s ADMA and arginine/total methylated arginine levels were 98 significantly lower (p=0.035 and p=0.049, respectively), while SDMA/ADMA, L-NMMA and arginine/ADMA levels (p=0.001, p=0.008 and p=0.017) increased, and no statistical difference was found for other parameters (p>0.05). When compared to group 3, ADMA, arginine, citrulline, methylated arginines and L-NMMA levels in group 2 (p=0.035, p=0.001, p=0.015, p=0.032, p=0.032) increased, while SDMA/ADMA levels (p=0.041) decreased. Conclusion: The decrease in arginine and ADMA levels in non-muscle invasive BC patients is thought to be promising, and these markers may be useful in monitoring the diagnosis and treatment of patients.