A scaffold toeboard system for locking a toeboard between two vertical scaffold members where each vertical scaffold member includes a tubular member having a diameter and an outer shape. The toeboard system includes a toeboard having an elongated member with a fixed terminating end and an adjustable terminating end. The toeboard further includes a front portion, a top portion, a bottom portion and a rear portion. The toeboard system further includes a locking mechanism slidably mounted to the adjustable terminating end, where the locking mechanism includes a lock member body with a front sidewall two fingers positioned on said locking mechanism and extending outwardly from the front sidewall of the locking member. The two fingers separated by a horizontal distance of about the diameter of a scaffold vertical member. The locking mechanism further includes a lock, where the lock is actuatable to fix the position of the lock member body with respect to the toeboard in a deployed position. The fixed terminating end is shaped to engage a scaffold vertical member.