Tumour-retained activated CCR7+ dendritic cells (DCs) are heterogeneous and regulate local anti-tumour cytolytic activity. This study investigates the spatio-temporal dynamics of CCR7+ DCs in anti-tumour immune responses using a photoconvertible mouse model and single-cell RNA sequencing (scRNA-seq). The findings reveal that CCR7+ DCs are the dominant population migrating to tumour-draining lymph nodes (dLN), but a subset remains tumour-resident despite CCR7 expression. These tumour-retained CCR7+ DCs are phenotypically and transcriptionally distinct from their dLN counterparts and become increasingly "exhausted" with prolonged tumour dwell-time. They co-localise with PD-1+ CD8+ T cells in human and murine solid tumours, and following anti-PD-L1 treatment, upregulate stimulatory molecules such as OX40L, thereby enhancing anti-tumour cytolytic activity. These data uncover previously unappreciated heterogeneity in CCR7+ DCs that may underpin a variable capacity to support intratumoural cytotoxic T cells. Dendritic cells (DCs) capture tumour antigens and upregulate the chemokine receptor CCR7, which directs their migration to secondary lymphoid organs where they present antigens to T cells. Two major conventional DC (cDC) subsets have been identified in tumours; cDC1 that specialise in cross-presenting tumour antigens to CD8+ T cells and are associated with improved survival, and cDC2 that present exogenous antigens to CD4+ T cells and have variable associations with cancer prognosis and treatment responses. The recent application of single-cell technologies to tissue samples has enabled the distinction of an activated DC state that may arise from both cDC1 and cDC2 but demonstrates a conserved phenotype and transcriptional programme characterised by the expression of LAMP3, genes consistent with a maturation and migration (CCR7, FSCN1, CD40), and immunoregulatory molecules including PD-L1 and PD-L2. This DC population has been variously labelled as "migratory DCs", "mature DCs enriched in immunoregulatory molecules" (mRegDCs), as well as "LAMP3+ DCs". "mature DCs", or "activated DCs". Regardless of nomenclature, single-cell atlasing efforts have identified activated CCR7+ DCs in multiple human cancer types, and the acquisition of this maturation programme appears dependent on the uptake of tumour antigens. Intriguingly, despite the conserved expression of co-inhibitory molecules such as PD-L1 in CCR7+ DCs, the expression of the DC activation-associated marker LAMP3 is associated with improved prognosis in breast, lungTumour-retained activated CCR7+ dendritic cells (DCs) are heterogeneous and regulate local anti-tumour cytolytic activity. This study investigates the spatio-temporal dynamics of CCR7+ DCs in anti-tumour immune responses using a photoconvertible mouse model and single-cell RNA sequencing (scRNA-seq). The findings reveal that CCR7+ DCs are the dominant population migrating to tumour-draining lymph nodes (dLN), but a subset remains tumour-resident despite CCR7 expression. These tumour-retained CCR7+ DCs are phenotypically and transcriptionally distinct from their dLN counterparts and become increasingly "exhausted" with prolonged tumour dwell-time. They co-localise with PD-1+ CD8+ T cells in human and murine solid tumours, and following anti-PD-L1 treatment, upregulate stimulatory molecules such as OX40L, thereby enhancing anti-tumour cytolytic activity. These data uncover previously unappreciated heterogeneity in CCR7+ DCs that may underpin a variable capacity to support intratumoural cytotoxic T cells. Dendritic cells (DCs) capture tumour antigens and upregulate the chemokine receptor CCR7, which directs their migration to secondary lymphoid organs where they present antigens to T cells. Two major conventional DC (cDC) subsets have been identified in tumours; cDC1 that specialise in cross-presenting tumour antigens to CD8+ T cells and are associated with improved survival, and cDC2 that present exogenous antigens to CD4+ T cells and have variable associations with cancer prognosis and treatment responses. The recent application of single-cell technologies to tissue samples has enabled the distinction of an activated DC state that may arise from both cDC1 and cDC2 but demonstrates a conserved phenotype and transcriptional programme characterised by the expression of LAMP3, genes consistent with a maturation and migration (CCR7, FSCN1, CD40), and immunoregulatory molecules including PD-L1 and PD-L2. This DC population has been variously labelled as "migratory DCs", "mature DCs enriched in immunoregulatory molecules" (mRegDCs), as well as "LAMP3+ DCs". "mature DCs", or "activated DCs". Regardless of nomenclature, single-cell atlasing efforts have identified activated CCR7+ DCs in multiple human cancer types, and the acquisition of this maturation programme appears dependent on the uptake of tumour antigens. Intriguingly, despite the conserved expression of co-inhibitory molecules such as PD-L1 in CCR7+ DCs, the expression of the DC activation-associated marker LAMP3 is associated with improved prognosis in breast, lung