Can a Texas landlord enter my apartment without notice?

No, that is not correct. While Texas Property Code does not specify a required notice period for landlord entry (unlike many other states), a landlord's unauthorized entry can constitute harassment or a breach of your quiet enjoyment — an implied warranty in every Texas residential lease. If you have a lease, check it for entry notice provisions. Practically, 24 hours written notice is the widely accepted standard. Document each unauthorized entry with dates and times. Send your landlord a certified letter requesting advance notice. If it continues, you may have grounds to terminate your lease without penalty or to seek damages in small claims court.