Kefir are mixed microorganisms cultures containing mainly lactic bacteria and yeast which are capable to ferment different substrates (milk, water sugar solution, fruit juice, etc.). Fermented beverage from kefir is slightly carbonated and alcoholic, with variable acidity, rich in nutrients (vitamins, polysaccharides, alcohol, etc.) and can present prebiotic and probiotic properties. The aim of this study was to evaluate the production of mixed passion fruit and cow milk beverages using two kefir cultures: one for milk (MK) and other for water sugar solution (WK). The cultures were evaluated through central composite rotatable designs (CCRD) with independent variables concentration of kefir (K, 3.6-6.4% w/w) and proportion passion fruit : milk (P:M, 0:100 – 100:0 % w/w). The evaluated responses were cellular growth (X), yield (Y), CO2 production, soluble solids (SS), total solids (TS), pH and acidity (A). The fermentations were conducted in room temperature, without agitation for 24 hours. The average values of fermentative parameters were: X = 24.8% (MK) and 37.0% (WK); Y = 92% (both), CO2 = 5.9% (MK) and 6.5% (WK). The increase of P:M reduced the MK growth and increase of K reduced CO2 production in WK. The average values of physical-chemistry parameters were: 10.0 – 10.3% ST; 9.3 – 9.6% SS; 0.72 – 1.08% A and 3.49 to 3.78 pH. The increase of P:M increased ST, SS and A and reduced pH. There was an average reduction of one unity of SS and pH after fermentation and the MK beverage showed higher acidity. The passion fruit and cow milk mixture was a viable substrate to kefir growth. The optimized conditions were: 4.0% K and 14.5:85.5 P:M (MK); 5.0% K and 50:50 P:M (WK). It means that a small addition of P improved MK growth and the addition of M improved WK growth.