The documentation of ethnobotanical knowledge is useful for biocultural conservation, preserving the diversity of plants, and drug development. The present study was carried out to compile and document the knowledge and uses of plants in Al Baha Province, Kingdom of Saudi Arabia (KSA). A total of 81 knowledgeable informants of different sexes, ages, and status levels were randomly selected and interviewed. The majority of the informants (63%) were > 60 years old. The collected data were qualitatively and quantitatively described using different quantitative indices [family importance value (FIV), use value (UV), and informant consensus factor (ICF)]. The fidelity level (FL), rank order priority (ROP), and relative popularity level (RPL) were determined for the plants (42 species) mentioned by at least three informants. A total of 97 plants belonging to 91 genera and 44 families were reported. The most commonly used parts were fruits (30.7%) and leaves (25.4%), whereas the most frequently used modes of preparation were maceration (24.7%) and direct application (23.3%). Most of the cited plants (49.5%) were traditionally used for gastrointestinal tract (GIT) disorders, whereas a few plants (6.2%) were used for the treatment of reproductive disorders. The most ethnobotanically important families were Lamiaceae (FIV = 0.35) and Apiaceae (FIV = 0.33). The highest UV was represented by Zingiber officinale (0.086) followed by Commiphora myrrha and Trigonella foenum-graecum (0.074). The level of agreement among the interviewees was remarkably high (ICF = 0.65–0.93) for plants that had the ability to cure infectious diseases. A low level of agreement (ICF = 0.33–0.48) was observed among the informants towards plants that were used to treat gastrointestinal tract, reproductive, hematological, and central nervous system disorders. There was a total and absolute disagreement (ICF = 0) among the informants regarding the plants that were used to treat renal, endocrine system, oncological/immunological, rheumatic, orthopedic, ear, nose, and throat (ENT), and inflammatory disorders. Six of the plants which were cited by three informants or more had a high healing efficacy (FL = 100) and forty species attained ROP values of 50 or above. Out of the 42 plants, 20 species were grouped as popular (RPL = 1), and the remaining plants (22 species) were unpopular (RPL < 1). Curcuma longa, which showed the highest ROP value (100), was used to enhance immunity. In conclusion, various plant species in Al Baha province were used by the local communities for the treatment of different health problems. The documentation of these plants could serve as a basis for further scientific research and conservation studies.