Background Oro-facial myofunctional praxis assesses the muscular coordination and the degree of motor impairment of the lingual, mandibular and facial muscles necessary for articulation, mimicry and swallowing. Purpose The objective of this study was to create and validate the MBLF protocol, a French oro-facial myofunctional assessment in order to quantify patient’s impairment and to specify the motor and functional deficit for an adapted management. Methods The MBLF was validated against the Sunnybrook Facial Grading System (criterion validity). The construct validity was tested by comparing healthy subjects (n = 102) from patients with facial palsy (n = 60). Internal and external consistency of face symmetry were reported. Normative data was provided. Results There was a statistically significant correlation between the MBLF protocol and the Sunnybrook Facial Grading System [F(59) = 310.51, p < 0.001, R2 = 0.843]. Significant differences were observed in Student’s t test between healthy volunteers and patients with facial palsy [t(74.13) = 14,704, p < 0.001, r = 0.863]. A significant effect of the severity grades of facial palsy on the MBLF_TOTAL scores was found [F(158) = 268.469, p < 0.001]. The more severe the facial palsy, the lower the motor scores were. Conclusion This MBLF French validation provides a baseline for comparing and quantifying the performance of subjects. The MBLF protocol is valid for assessing facial symmetry in peripheral facial palsy. A prospective study is needed to validate its role in dynamic evaluation of facial palsy.