Leptospirosis is an important zoonotic disease in paddy field with 29.5% prevalence rate in Mazandaran province and 4% to 52% mortality rate among hospitalized patients. Prevention is an important strategy for the control of this disease. This study aimed to compare the prophylactic effect of azithromycin versus doxycycline against leptospirosis in an endemic area in north of Iran. In this randomized double-blind placebo-controlled trial, paddy field workers (n = 187) were randomized to receive azithromycin (500mg weekly), doxycycline (200 mg weekly) or placebo starting one week before exposure to paddy field, during and to four weeks after. Paddy field workers aged 18- 65 years who signed the informed consent form were assessed for signs and symptoms of leptospirosis in addition to serologic evidence of the disease 6th and 12th week. Data were analyzed with SPSS version 13 using Chi-square and Fisher exact test and ANOVA. From June to September 2016, 187 participants were entered the study to receive azithromycin (n = 66), doxycycline (n = 71) or placebo (n = 50). In terms of preventing against clinical leptospirosis, there was not any significant difference between three arms, though there was statistically significant difference of seropositivity after 6 and 12 weeks in comparison to baseline among all three groups (P = 0.029) and between active treatment (eg. azithromycin and doxycycline) groups and placebo group (P = 0.01). Azithromycin like doxycycline decreased seropositivity without significant effect on clinical leptospirosis.