The Cathedral in Varaždin, one of the most significant early baroque sacral buildings in the northern part of Croatia, was built from 1642 to 1646 by the Jesuit fathers, an order very much accredited for the revival of the Catholic Church in the 16th and 17th centuries who settled in Varaždin in 1632 and began a grammar school there in 1636. The designer and project manager of the cathedral was allegedly the Jesuit Juraj Matota, while the construction costs were financed by the count Gašpar Drašković. This is an early baroque single-nave church with flanking chapels and two galleries above them.

The sacristy was decorated and completed in 1656. Its final form was attained through reconstruction work in 1726. The bell tower, completed in 1676, with its corner pilasters was an innovation widely used later in the 18th century. The portal is considered the most modern stylistic portal in Croatia of the 17th century. The three-quarter sized semi-pillars on high bases hold a gable which opens towards an ornamented niche, in which, on the volute pedestal a statue of Virgin Mary stands. On its base, on the beam, hanging on the iron hook, there is a coat of arms of the Drašković family, who continued to be main patrons of the church after the count Gašpar.

The former Jesuit College, which today is the seat of the Faculty of Organisation and Information Technology erected from 1679 to 1691, and the former Jesuit grammar school, currently the Chancery of the Diocese of Varaždin, which started in 1680, along with the church, make up what is considered the best and most precious early-baroque architectonic and urban project in Varaždin.

Contrasting the reserved and dignified simplicity of its outer appearance, the inner part of the church is very ornamental. The main altar, third in the row, was completed in 1737. Its monumental size extends over the entire width and height of the sanctuary. On top of the high and massive pedestal, a two-storey high altarpiece rises. On the lower level, at the centre, is an altar picture of the Assumption of the Blessed Virgin Mary, inspired by similar compositions of paintings by Rubens, Titian and Reni. On its left and right, among the pillars, there are statues of the first apostles St. Peter and St. Paul, the Jesuit saints St. Ignacius of Loyola and St. Francis Xavier and St. John Nepomucene and St. Donatus. On the upper floor, the central picture of St. Joachim and St. Anne with statues of the four evangelists divides the scene of the Annunciation: the B.V. Mary on one side and the Archangel Gabriel on the other. Two flying angels look towards the Holy Trinity at the top of the altarpiece. On the communion table there is a tabernacle with carved ornaments repeating the main motif of the altarpiece with its small pillars and composition.

On the pulpit, ordered in Graz in 1761, today there exists only a lectern with rococo features showing a relief of the scene of the Storm at Sea. The baldachin, destroyed in the fire in 1776, was replaced by a more classic structure in the 19th century.

The first organ dating from 1649, burned up in 1665, after which new one was bought. This organ was replaced in 1747 by a new one constructed by an organ builder in Varaždin, Josip Papa, junior. When this one was worn out, a new organ was ordered from J. Brandl in Maribor, yet the old closets and positives, that served as ornaments were kept. From 1988 to 1998 the organ builder Wolfgang Braun constructed the current organ that has 54 sound registers and a large number of free combinations and connections. The new three-part prospect still shows an old central closet from the 18th century.

Upon abolishment of the Jesuit Order in 1773 the church was taken over by the Pauline Fathers in 1776 who made a new façade with a relief of the Holy Trinity in 1777. After their abolishment in 1786, the church was secularised and in 1788 turned into a grain silo for the military. In 1797 it was blessed again for liturgical use and given to the grammar school whose priests-teachers administered the church until 1949.

The Chapter of Canons of Čazma that settled in Varaždin in 1810/11 was granted the church as its collegiate church in 1954 and the Bull of Pope John Paul II Clarorum sanctorum dated 5 July 1997, proclaimed this church as the Cathedral of the newly erected Diocese of Varaždin.

The church was damaged in the fires of 1650, 1665, 1776, 1818 and was reconstructed in 1653, 1671, 1698, 1756, 1777, 1818, 1875, 1900, 1937. From 1982 to 1995, the church was professionally renovated in detail, inside and out. Besides the Restoration Institute of Croatia, who executed the works, Msgr. Alojzije Domislović, canon of the collegiate church at that time, the City of Varaždin and the Ministry of Culture are also to be credited for this undertaking.

As a gift of the Kolping Family of the Archdiocese of Paderborn, the Cathedral received in 1998 a new altar, two pulpits and a candleholder for the Easter candle. All this was made by Johannes Roebbecke in the style of a large altar, made from two-hundred year old oak from Westphalia, north-western Germany.

For the fifth anniversary of the Diocese in 2002, two new bronze doors were built, which were made by Professor Hrvoje Ljubić. In the rosetta there is a relief of the Assumption of the Blessed Virgin Mary to heaven, the Queen of Heaven and Earth, while at her left and right are Blessed Alojzije Stepinac and St. Marko Križevčanin, patron saints of the Diocese. In the four panels of the upper part of the door wings there are relief scenes from Mary's life, and in the four lower panels there are scenes from the shrines of Our Lady of Lepoglava, Močile and Sveti Juraj na Bregu, as well as the shrine of the Precious Blood of Jesus in Ludbreg. The rosetta is divided from the panel on the door by a Latin inscription: The Diocese of Varaždin, erected on 5 July 1997. The upper panels are separated from the lower panels by handles in the form of Greek crosses that contain the coat of arms of Pope John Paul II, who erected the Diocese of Varaždin and of Msgr. Marko Culej, its first Bishop. Beside the handles, there are also their Episcopal mottos.

The famous Croatian and Kajkav dialect writer, Rev. Juraj Habdelić S.J., wrote in his Zercalo Marijansko (Mary's Mirror), published in Graz in 1662, regarding the church of the Assumption of the Blessed Virgin Mary in Varaždin: There are surely none that match it in the entire Slavonic Kingdom, except for the Cathedral of Zagreb.

The new Jesuit church and its first five altars were consecrated by the Bishop of Zagreb Petar Petretić on 28 May 1656. Upon the desecration of the church in 1787, it was blessed again for liturgical use on 1 May 1797, by Ivan Ivanović, the parish priest of Vinica and canon of the Chapter of Čazma 

The church of the Assumption of the Blessed Virgin Mary and ten other churches and chapels in Varaždin gave the city already in the 18th century the name of  "Little Rome"

The Cathedral has several tombs where no one has been buried since the 19th century. In front of the main altar there is a Jesuit tomb and all the side chapels have their tombs as well. The crypt of the noble family Drašković is in the chapel of the Mother of God of Loreto, at the left of the main entrance

The most recent professional and detailed reconstruction work was completed from 1982 to 1995, and was managed by the Restoration Institute of Croatia and through the care and efforts of Alojzije Domislović, a canon lawyer and dean of the Chapter of Canons of Čazma and Varaždin

Having first being assigned to the Jesuits (1642-1773), then to the Paulines (1776-1786), then to the Grammar School (1797-1949) and finally to the Chapter of Canons of Čazma (1954-1997), the church of the Assumption of Virgin Mary became the Cathedral of the newly founded Diocese of Varaždin on 5 July 1997