•Calcium nitrate was found to be a suitable healing agent for autonomous crack-sealing.•The use of microcapsules significantly increased the self-healing efficiency.•The healing products were mainly calcium carbonate.•The largest crack width healed was up to 290 µm. Self-healing concrete through microencapsulated calcium nitrate was evaluated for its crack-sealing efficiency. The evaluated variables in this study were the microcapsule size, concentration (by weight of cement), and capsule shell properties. The production parameters for the microcapsule preparation were adjusted to control the shell properties and mean particle diameter accordingly. The results showed that all microcapsule-containing specimens had significantly higher healing efficiencies than the control groups after 21 and 42 days of healing. As the crack sizes increased, the microcapsule-containing specimens maintained a higher healing efficiency than the control groups.