The present disclosure is drawn to inertial pumps. An inertial pump can include a microfluidic channel, a fluid actuator located in the microfluidic channel, and a check valve located in the microfluidic channel. The check valve can include a moveable valve element, a narrowed channel segment located upstream of the moveable valve element, and a blocking element formed in the microfluidic channel downstream of the moveable valve element. The narrowed channel segment can have a width less than a width of the moveable valve element so that the moveable valve element can block fluid flow through the check valve when the moveable valve element is positioned in the narrowed channel segment. The blocking element can be configured such that the blocking element constrains the moveable valve element within the check valve while also allowing fluid flow when the moveable valve element is positioned against the blocking element.