Pop star-turned-fashion designer Beckham was feted with the Best Brand prize during a ceremony at London's Coliseum venue.
The former Spice Girls star, who was escorted to the event by husband David just two days after he was involved in a car crash, was emotional as she accepted the trophy.
She said, "Wow, thank you. I am so, so proud to be British and incredibly proud to have built my brand in the Uk. I want to thank my team. I love you all so much and this is for all of you."
She also had special praise for her husband and family, adding, "We've come a long way since that Spice Girls dressing room. David, you inspire me every day. You support me. You make this possible. I adore you and my children. And my parents, you love me unconditionally - and I know I am a pain in the bottom."
Harry Potter star Watson was presented with the British Style Award by One Direction singer Harry Styles, who claimed the prize last year (13).
Seeing off tough competition from the likes of Kate Moss, David Beckham, and George Clooney's new wife Amal Alamuddin, Watson thanked the British fashion industry for being "supportive of my career" and "allowing me to reinvent myself."
Poppy Delevingne joined fellow models Karlie Kloss and Joan Smalls in handing little sister Cara Delevingne the Model of the Year prize, and U.S. Vogue editor Anna Wintour was feted for her years of contributions to the fashion industry with the Outstanding Achievement award.
Among the other attendees at the star-studded event were Rihanna, Rita Ora, Anna Kendrick, Lily Allen, Suki Waterhouse, Kylie Minogue, and Nicole Scherzinger.