Katharina, die am 15. April 1662 Lissabon verlassen hatte, traf am 13. Mai 1662 mit ihrer großen portugiesischen Gefolgschaft in Portsmouth ein. "The voyage was tedious and stormy; in the channel it blew such a gale, that the fleet sought shelter in Mount Bay, till the storm subsided, and a favourable breeze sprung up. Off the Isle of Wight, they met the Duke of York [Jakob II. (VII.) Stuart, den jüngeren Bruder des englischen Königs], who, at the head of five frigates, had put to sea, to meet the future sister-in-law. … he daily visited the Queen to the end of the voyage … The fleet anchored at Spithead on the thirteenth of May; and on the same day Katherine landed, and was conducted to the King’s house, at Portsmouth ..." (in: Francis Lancelott: The Queens of England and their Times, Volume II, id., p. 713). In ihrem neuen Königreich war sie als Katholikin nicht beliebt. Ihren Gatten, den englisch-schottischen König Karl II. Stuart, liebte sie sehr, aber seine vielen außerehelichen Affären taten ihr sehr weh. Trotzdem war sie gegenüber seinen vielen unehelichen Kindern stets sehr freundlich. Sie selbst erlitt in den 1660er Jahren zwei Fehlgeburten und blieb ohne ein eigenes Kind.
Karl II. Stuart hatte London am 19. Mai 1662 verlassen und traf einen Tag später in Portsmouth ein. Er schrieb an Edward Hyde: "It was happy for the honour of the nation I was not put to the consummation of the marriage last night, for I was so sleepy, by having slept but two hours in my journey, that I was afraid that matters would have gone very sleepily. I can only now give you an account of what I have seen a-bed; which, in short, is; her face is not so exact as to be called a beauty, though her eyes are excellent good, and not anything in her face that in the least can shock one. On the contrary, she has much agreeableness in her looks altogether as ever I saw; and, if I have my skill in physiognomy, which I think I have, she must be as good a woman a ever was born ... You would much wonder to see how well we are acquainted already." ... "The couple was married on 21 May [ganz früh am Morgen], secretly according to Catholic rites for the Queen's sake, and publicly by the Bishop of London [am Abend]." (in: Christopher Falkus: The Life and Times of Charles II, p. 90). "After dinner, the ceremony was publicly solemnized, after the form established by the Church of England, in the great hall or presence chamber, by the Bishop of London. … When the King and Queen had taken their places under a rich canopy, the Bishop performed the nuptial rites prescribed in the Book of Common Prayer, and pronounced them married … 'Long may they live!' responded the spectators, with hearty shouts; and, in conclusion, the ribbons, which the bride wore in profusion, were cut from her dress, and distributed in small portions, as wedding favours, amongst the assembly." (in: Francis Lancelott: The Queens of England and their Times, Volume II, id., p. 713). "Catherine could speak no English, and her convent upbringing scarcely equipped her for the court of the merry monarch. Her retinue of monks and forbidding-looking ladies caused much amusement to the gay courtiers who surrounded the King." (in: Christopher Falkus: The Life and Times of Charles II, p. 90).
Die hohen adligen Damen einschließlich der Königstöchter hatten in Portugal eine sehr strikte Erziehung. Ihr steifes Verhalten, ihre großen Haarlocken an der Stirn, die breiten Röcke sorgten für Aufsehen in England und: "They [diese hohen adligen Hofdamen und Katharina von Braganza] refused to go out of doors, for fear they might be seen by men, and would not even consent to sleep in any lodgings, without first ascertaining if they had previously occupied by any of the other sex." (in: Julia Mary Cartwright Ady: Madame, a life of Henrietta, daughter of Charles I. and Duchess of Orleans, id., p. 120).
Die Hochzeitsnacht: "The Queen's [Katharina von Braganza] state of health did not permit the marriage to be consummated that night [sie hatte die Regeln.] The King jokingly reported to his sister Madame [seine jüngste Schwester Henriette Anna] that he thought it was just as well that the long sea journey had upset her cycle, for he himself had such a terrible journey down to Portsmouth that he was afraid that 'matters would have gone stupidly'. [Er hatte an diesem Tag nur zwei Stunden geschlafen und fühlte sich körperlich nicht fit, die Ehe zu vollziehen; es war also gut, dass Katharina von Braganza ebenfalls nicht in der Lage war, ihre Ehe vollziehen zu lassen]." (in: Antonia Fraser: King Charles II, id., p. 206).
Die ersten zwei bis drei Monate in ihrer Ehe: "During the next two or three months, the King was entirely taken up with his wife. Her sweetness and naiveté pleased him; her very ignorance tickled his fancy. He forgot his mistress for the time, and was as well amused as a child with a new toy. But, before long, Lady Castlemaine resumed her old influence, and, when he insisted on forcing the Queen to receive her at Court, Clarendon had to remind him how strongly he had blamed the conduct of Louis XIV., in allowing La Vallière to live under Madame's roof, and appear in his wife's presence. Charles had even been heard to say that 'he should never be guilty of such a piece of ill-nature, for, if ever he could be guilty of keeping a mistress after he had a wife, she should never come where his wife was.'" (in: Julia Mary Cartwright Ady: Madame, a life of Henrietta, daughter of Charles I. and Duchess of Orleans, id., pp. 120-121).
Katharina von Braganza war aber nicht bereit, Barbara Villiers, Lady Castlemaine, die bekannte Geliebte ihres Gatten, als ihre Hofdame zu akzeptieren. Diesen Kampf verlor sie allerdings gegenüber ihrem Gatten: "In this struggle Charles used a variety of tactics. Once he openly introduced his mistress at court, and when Catherine learnt who it was who had just kissed her hand she fainted. Then Charles began to ignore her, and plunged himself even more vigorously into his other pleasures. He had her Portuguese ladies sent home, and left her an isolated figure, friendless and helpless in her misery. Then, quite suddenly, Catherine gave up the unequal fight and not only accepted Lady Castlemaine [Barbara Villiers] but went out of her way to pay her compliments and cultivate her as a friend. She began to compete for the King's affections, cutting her dresses lower and her skirts shorter, Charles responded, and for the rest of the reign domestic harmony prevailed." (in: Christopher Falkus: The Life and Times of Charles II, pp. 90-91).