Lord Krishna is the original creator and Lord Brahma is the secondary creator.
“The Vedanta-sutra begins by declaring that the Absolute Person is the original source of all creation (janmady asya yatah). One may ask whether Lord Brahma is the Supreme Absolute Person. No, the Supreme Absolute Person is Krishna. Brahma receives his mind, intelligence, materials and everything else from Krishna, and then he becomes the secondary creator, the engineer of this universe. In this regard we may note that the creation does not take place accidentally, because of the explosion of a chunk. Such nonsensical theories are not accepted by Vedic students. The first created living being is Brahma, who is endowed with perfect knowledge and intelligence by the Lord. As stated in Srimad-Bhagavatam, tene brahma hrda ya adi-kavaye: although Brahma is the first created being, he is not independent, for he receives help from the Supreme Personality of Godhead through his heart. There is no one but Brahma at the time of creation, and therefore he receives his intelligence directly from the Lord through the heart.
Lord Brahma is described in this verse as the original cause of the cosmic manifestation, and this applies to his position in the material world. There are many, many such controllers, all of whom are created by the Supreme Lord, Vishnu. This is illustrated by an incident described in Chaitanya-caritamrta. When the Brahma of this particular universe was invited by Krishna to Dvaraka, he thought that he was the only Brahma. Therefore when Krishna inquired from His servant which Brahma was at the door to visit, Lord Brahma was surprised. He replied that of course Lord Brahma, the father of the four Kumaras, was waiting at the door. Later, Lord Brahma asked Krishna why He had inquired which Brahma had come. He was then informed that there are millions of other Brahmas because there are millions of universes. Krishna then called all the Brahmas, who immediately came to visit Him. The catur-mukha Brahma, the four-headed Brahma of this universe, thought himself a very insignificant creature in the presence of so many Brahmas with so many heads. Thus although there is a Brahma who is the engineer of each universe, Krishna is the original source of all of them. ”
Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), “Srimad Bhagavatam”, Seventh Canto, Chapter 03 – Text 28
