Almost 28,000 people had to wait over 12 hours in hospital emergency departments from January to June 2019.
The new figure shows that waiting times are 4 times what they were 5 years ago within the same 6 month period.
12 hours is the targeted time that no one should exceed to be discharged, transferred or to be treated.
The health minister said 12 hour waits fell last month but he expects health boards to deliver better performance.
Figures that have been published by the NHS Wales Informatics Service shows an flowing increase since 2014 on individuals who have exceeded the 12 hour target.
June shown, more than 4,000 patients had long waits - 3.1% of patients - with the highest numbers at Morriston in Swansea (616), Glan Clwyd (609) and Wrexham Maelor hospital (526 patients).
Dr Jo Mower, vice president of the Royal College of Emergency Medicine in Wales, said: "Today's data shows that poor performance is a year-round reality in Wales."
Health Minister Vaughan Gething said the total number of patients attending A&E had passed 520,000 at the year's halfway point.
"I am still concerned about the timeliness at a small number of sites but we are working with them to improve performance," he added.
The Welsh Government said an extra £50m given to help reduce the longest waiting times for elective operations was starting to have an impact.
Latest figures show a 19% reduction in waits over 36 weeks compared with the same period last year.
Meanwhile, Mr Gething said he has written to the UK government calling for urgent action to resolve concerns of medical staff over pension and tax implications that are leading to some not undertaking additional hours.
Demie Haywood is a local newsreader at Bro Radio 98.1fm