One of the items was a Poundland iPhone 5 or 6 charger cable, sold in its stores for just £1 instead of the £15 charged by Apple.
Accompanied by staff, several of whom weren't even born when the first Poundland store opened in Burton upon Trent, chief executive Jim McCarthy also planted a Macmillan Nurse rose bush to mark the company's strong links with the cancer charity. Poundland and its staff have raised £1.3 million for Macmillan Cancer Support over the last seven years.
Mr McCarthy also released 25 balloons in Poundland green to mark the event.
He told staff : "I know you will be as proud as I am of what has been achieved over the last 25 years."
Earlier this year, the company revealed it broken the £1 billion sales barrier, serving more than 5.5 million customers every week.
Mr McCarthy reminded staff that 1990 was also the year of Gazza's tears at the football World Cup in Italy as well as Richard Gere and Julia Roberts starring in the movie Pretty Woman. A Gazza poster and a Pretty Woman soundtrack CD were among the items in the time capsule.
The year 1990 also saw the first Poundland store opened at Burton's Octagon Centre, where it sold 13,000 products for £1 each on its first day.
"Burton customers knew they were on to something amazing and since then Poundland has become a familiar household name with nearly 600 stores in the UK, the Republic of Ireland and now another six Dealz in Spain," said Mr McCarthy.
Another three Spanish stores – which use the same name as Poundland's Irish shops because they deal in euros rather than pounds – are due to open in the next few months.
Giving Mr McCarthy a helping hand during the ceremony where two Poundland staff who almost share the company's birthday.
Sarah Burrell, from Bournville in Birmingham and a member of the firm' human resources department, was born in November 1990, while Amo Mann from Wolverhampton, who works on Poundland's online team, was born on December 8 - just five days before the Burton upon Trent store opened its doors.
Joining in the celebration were a team from Macmillan Cancer Support, including partnership manager Sharon Cottam who has worked with Poundland on its fundraising efforts since 2008.
Among the items buried for posterity in the time capsule were a Poundland staff t-shirt, a Macmillan pin badge, items from the store's Jane Asher bakeware and Tommy Walsh DIY ranges along with pictures of staff and stores, including the first one at Burton upon Trent.
It also included a pair of floppy discs from the 1990s, a yo-yo, popular toys of the time including a Tamagochi and a Teenage Mutant Ninja Turtle, a couple of newspapers and a CD of the Pretty Woman movie soundtrack.
Poundland was the creation of former Black Country market trader Steve Smith and his father. They built the current headquarters and expanded the chain to 74 stores before selling up for £50 million in 2002.
Mr McCarthy was hired to run the business in 2006 and since then it has more than tripled in size. He has said he wants to see Poundland expand to 1,000 stores in addition to the 251 branches Poundland hopes to acquire in its £55 million takeover of 99p Stores.