Abstract Plant-derived exosome-like nanoparticles (PDENs) have been paid great attention in the treatment of ulcerative colitis (UC). As a proof of concept, we isolated and identified Portulaca oleracea L-derived exosome-like nanoparticles (PELNs) from edible Portulaca oleracea L, which exhibited desirable nano-size (~ 160 nm) and a negative zeta potential value (-31.4 mV). Oral administration of PELNs effectively suppressed the expressions of pro-inflammatory cytokines (TNF-α, IL-6, IL-12, and IL-1β) and myeloperoxidase (MPO), increased levels of the anti-inflammatory cytokine (IL-10), and alleviated acute colitis in dextran sulfate sodium (DSS)-induced C57 mice and IL-10^−/− mice. Notably, PELNs exhibited excellent stability and safety within the gastrointestinal tract and displayed specific targeting to inflamed sites in the colons of mice. Mechanistically, oral administration of PELNs played a crucial role in maintaining the diversity and balance of gut microbiota. Furthermore, PELNs treatment enhanced Lactobacillus reuteri growth and elevated indole derivative levels, which might activate the aryl-hydrocarbon receptor (AhR) in conventional CD4⁺ T cells. This activation downregulated Zbtb7b expression, leading to the reprogramming of conventional CD4⁺ T cells into double-positive CD4⁺CD8⁺T cells (DP CD4⁺CD8⁺ T cells). In conclusion, our findings highlighted the potential of orally administered PELNs as a novel, natural, and colon-targeted agent, offering a promising therapeutic approach for managing UC. Graphic abstract Schematic illustration of therapeutic effects of oral Portulaca oleracea L -derived natural exosome-like nanoparticles (PELNs) on UC. PELNs treatment enhanced Lactobacillus reuteri growth and elevated indole derivative levels, which activate the aryl-hydrocarbon receptor (AhR) in conventional CD4⁺ T cells leading to downregulate the expression of Zbtb7b, reprogram of conventional CD4⁺ T cells into double-positive CD4⁺CD8⁺T cells (DP CD4⁺CD8⁺ T cells), and decrease the levels of pro-inflammatory cytokines.