Abstract Asphaltene precipitation and deposition may cause severe problems during production, transportation and processing of crude oil, hence affecting efficiency and cost of production in both upstream and downstream operations. During crude oil production they can deposit in rock reservoir pores, thus leading to possible blocking and formation damage. Despite significant research asphaltene deposition under flowing conditions remains barely understood. Here, capillary flow experiments were conducted to study asphaltene deposition by examining the pressure drop across the capillary as a function of different factors. Asphaltenes were precipitated with n-heptane from a crude oil/toluene mixture. Increasing the precipitant fraction led to greater precipitation which results in a faster deposition rate. A higher total volumetric flow rate also led to a higher deposition rate and a higher mass of deposited asphaltenes with more asphaltenes deposited at the entrance of the capillary. This was confirmed by images taken with a confocal laser-scanning microscope. Diffusive boundary layer theory was considered to explain the results which predict that the effective diffusive boundary layer thickness grows with the mean velocity ūs1/3, whereas our results showed a dependence on ū.