Candidiasis is the most commonly encountered fungal infection, and oral candidiasis is often observed as a local opportunistic infection. Oral candidiasis is clinically divided into three types: acute forms, chronic forms, and Candida-associated lesions. Candida adhesion and multiplication are largely regulated by the local and systemic factors of the host. The local factors include impairment of the oral mucosal integrity, which is usually impaired by hyposalivation, anticancer drugs/radiation for head and neck cancers, denture wearing, a decrease in the oral bacterial population, and poor oral hygiene. Among Candida species, oral candidiasis is mostly caused by Candida albicans (C. albicans), C. glabrata, or C. tropicalis. Oral Candida induces a variety of symptoms, such as oral mucosal inflammation manifesting as an uncomfortable feeling, pain, erythema, erosion, taste abnormalities, and hyperplasia of the oral mucosa. Candida overgrowth in the oral cavity may disseminate to distant organs. Therefore, in order to avoid the sequelae of systemic candidiasis, oral candidiasis should be rapidly controlled. Oral candidiasis is usually treated by the local application of antifungal drugs. However, oral candidiasis occasionally escapes the control of such local treatment due to the development of multi-drug resistant Candida strains and species or due to the suppression of salivation or cellular immune activity. When drug-resistant strains are suspected as the pathogens and when the host is generally compromised, the oral administration of combinations of antifungal drugs, enhancement of cellular immune activity, and improvement of the nutritional condition are recommended.