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As an important member of mitogen-activated protein kinase (MAPK) cascades, MAPKs play an important role in plant defense response against biotic and abiotic stresses; however, the involvement of the majority of the MAPK family members against <i>Ralstonia solanacearum</i> and heat stress (HS) remains poorly understood. In the present study, CaMAPK1 was identified from the genome of pepper and its function against <i>R. solanacearum</i> and HS was analyzed. The transcript accumulations of <i>CaMAPK1</i> and the activities of its native promoter were both significantly induced by <i>R. solanacearum</i> inoculation, HS, and the application of exogenous hormones, including SA, MeJA, and ABA. Transient expression of <i>CaMAPK1</i> showed that CaMAPK1 can be targeted throughout the whole cells in <i>Nicotiana benthamiana</i> and triggered chlorosis and hypersensitive response-like cell death in pepper leaves, accompanied by the accumulation of H₂O₂, and the up-regulations of hormones- and H₂O₂-associated marker genes. The knock-down of <i>CaMAPK1</i> enhanced the susceptibility to <i>R. solanacearum</i> partially by down-regulating the expression of hormones- and H₂O₂-related genes and impairing the thermotolerance of pepper probably by attenuating <i>CaHSFA2</i> and <i>CaHSP70-1</i> transcripts. Taken together, our results revealed that CaMAPK1 is regulated by SA, JA, and ABA signaling and coordinates responses to <i>R. solanacearum</i> infection and HS in pepper.