Mercado will take over the highly acclaimed 9 o'clock edition of 'Newsroom,' currently anchored by Mitzi Borromeo.
The news anchor is said to be eyeing an exit from the local CNN station to pursue an advanced degree.
The morning program will be one of the first casualties from the ESPN deal.
The move represents a homecoming for Araullo, who prior to becoming a household name at ABS-CBN hosted the now-defunct '24 Oras' segment 'ATOMic Sports.'
Jarin-Bennett has officially been appointed this October.