Here's info from the club:
Celtic Tickets Go On Sale Tuesday, June 1Tickets go on sale Tuesday, June 1, for the summer friendly between Sounders FC and Scotland's Celtic on July 18 on the Xbox Pitch at Qwest Field. It will be Seattle's second friendly and, along with last week's Boca Juniors friendly, is part of the 18-match season-ticket holder package. A third match will be announced soon. Tickets will be available at www.SoundersFC.com, all Ticketmaster outlets, the Qwest Field Box Office, or by calling 800-745-3000. Celtic is making its fourth trip to Seattle and its third to Qwest Field. Winners of a record 34 Scottish cups and 42 league championships, the "Bhoys" from Glasgow boast a huge worldwide fan base. They are instantly recognizable for their green-and-white hooped jerseys. Celtic was the first British club to win a European championship in 1967. It met the NASL Sounders in 1981, and returned to face Manchester United in 2003 and Chelsea in 2004.