Armed police were seen detaining the suspect near to the scene of the Westminster terrorist attack in March.
No one was reported injured in the incident. Police confirmed a Taser was discharged after the male appeared to reach for a knife.
The Carriage Gates entrance to Parliament were temporarily closed while police dealt with the incident.
- Earlier this month reports claimed the Islamic State leader had been killed in Raqqa.
- Ledura Watkins was just 20 when he was wrongly convicted for shooting a teacher.