Circadian rhythms are biological cycles of approximately 24 h that regulate various processes in living organisms, aligning them with day-night cycles for optimal resource use and stress management. In addition to plants and other higher organisms, such rhythms also exist in the rhizomicrobiome. Circadian rhythms support bacteria in photosynthesis, nitrogen fixation, and hydrogenase activity. The synchrony between the rhythms of plants and rhizomicrobiome benefits both the host plant and rhizobacteria. Circadian rhythms support bacteria in photosynthesis, nitrogen fixation, and hydrogenase activity. Plant circadian oscillators can influence the structure of the rhizomicrobiome, possibly through changes in plant development or root exudation patterns. Twenty-four-hour fluctuations occur in the rhizosphere microbiome under both light–dark cycles and constant conditions, with different plant genotypes recruiting distinct microbial communities. This indicates a potential signaling of circadian timing from plants to their microbiomes. Additionally, some soil microbes exhibit rhythmic behavior even in the presence of arrhythmic plants, suggesting an intrinsic circadian rhythmicity within the rhizomicrobiome itself that directly or indirectly affects plant growth. Given that circadian clocks are known in fungi, nematodes, and various bacteria, these findings highlight the potential role of circadian rhythms in shaping plant–microbe interactions and microbial community dynamics in the rhizosphere.