Watson is ranked junior 23 in the world
Heather Watson and her doubles partner Ajla Tomljanovic are the top seeds in the International Casablanca Junior Cup 2009 in Tlalnepantla, Mexico City.
Guernsey's Watson, 16, has teamed up with the Croatian player for the Grade A tournament.
In the first round they face the pairing of Alina Jerjomina, of Latvia, and Russia's Julia Samuseva.
Watson, ranked junior 23 in the world, is seeded fifth in the singles and beat Koritza Beneditt in the first round.
She won 6-0 6-0 and will play Melissa Bolivar of Colombia in round two.
After the tournament, Watson will travel to Australia to take part in two further events, including the Australian Junior Open.