To analyze conjugate effect under partially heated condition, two-dimensional numerical study is performed for single-phase laminar flow through microtubes. Constant heat flux is applied on outer surface along the heating length of the microtube. For partial heating, the microtube is divided into three parts of 6 mm (L1), 48 mm (L2) and 6 mm (L3). Three cases are considered for partial heating: (a) insulated across L1 and L3 and heating across L2, (b) insulated across L1 and heating across L2 and L3 and (c) insulated across L3 and heating across L1 and L2. For direct comparison, heating across full length of the microtube is also considered. Parametric variations include microtube wall thickness to inner radius ratio (δsf), and solid to fluid conductivity, ratio (ksf) and flow Re. Presence of axial wall conduction is assessed in terms of dimensionless wall temperature and heat flux at the solid–fluid interface, dimensionless bulk fluid temperature, and local and average Nusselt number. The results indicate that there exists an optimal value of average Nusselt number for certain value of ksf at which dominance of axial wall conduction is smaller. Additionally, to highlight the effect of axial wall conduction, local heat flux distribution at the solid–fluid interface is also explored. © 2021, Indian Academy of Sciences.