A method is provided for contactless optical detection of yarn at a workstation of a textile machine in which the yarn moves in a sensing slot between a source of radiation and an optical sensor having at least one row of radiation sensitive elements, whereby shading of the individual radiation sensitive elements by yarn moving through the sensing slot is monitored and a state of the yarn is evaluated on a basis of the monitoring. The method monitors and evaluates a position of the yarn in the sensing slot or a time course of the position of the yarn in the sensing slot. A change is detected in the position or in the time course of the position of the yarn in the sensing slot corresponding to a yarn break before an end of the yarn break passes through the sensing slot. When the yarn break is sensed, a stop signal is generated for the workstation.