The 31-year-old's first call-up to the international team followed his wife giving birth to his first daughter and third child, on what the striker called a 'special day'
The 31-year-old welcomed Bella Rose into the world at 4:30 in the morning, only to find out he was in Roy Hodgson's squad hours later.
He told the club's official website: "It's been a special day and I'm trying to absorb what's happened. It's hard to describe how I'm feeling, if I'm being honest. Today has been a bit of a blur because there are a few things that have happened in my life and I'm trying to take them in.
"I was obviously already over the moon about the birth of my daughter - she was born at half-past-four this morning, and she's doing fine and so is the mother. And I'm absolutely delighted to be involved with England. It's the dream I've been fighting for and hoping for all my life.
"I don't think I'll be forgetting this [day] any time soon."
Lambert's journey to the England squad has been a long one. Spells at Blackpool, Macclesfield, Stockport, Rochdale and Bristol Rovers preceded his move to the Saints in 2009.
His goals helped them move up the leagues eventually into the Premier League, where he continued to find the net, finishing joint-top English goalscorer with Frank Lampard with 15 goals.
Lambert continued: "For most of my career I didn't think it'd ever happen but, for the last year or so, I thought there might be a slight chance so to get the call-up has been a dream come true.
"I'm over the moon just to be involved, but I want to make a claim and show that I'm here for the future. Obviously I understand my age means I'm not going to be there for the long term, but I am hoping that I can bring something to the squad over the next year or so.
"I am just concentrating on being at the top of my game, and if I can help [England] then that'll be brilliant."
England manager Roy Hodgson was thrilled to name him in his squad, and had at one point considered signing him when he was in charge of Fulham.
He is under no illusions the task ahead of the striker, but is delighted he can offer the opportunity to him
Hodgson said: "He deserves it because he has ploughed a very difficult furrow to get this far and wherever he has gone he has done extremely well.
"If Rickie Lambert can help us qualify, I will quite happily turn a blind eye to the fact that he is 32 at that time because it's not age that plays football, it's human beings."