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Although large-spored <i>Alternaria</i> species of the section <i>Porri</i> are considered to be the major agents responsible for leaf spot and blight of <i>Solanaceae</i>, small-spored <i>Alternaria</i> species are also frequently isolated from symptomatic tissues. A survey of the north-western regions of Algeria during the 2017–2018 growing seasons revealed that amongst the 623 <i>Alternaria</i> isolates from tomato, potato, pepper, eggplant and black nightshade, 8% could not be morphologically assigned to either section <i>Porri</i> or section <i>Alternaria</i>. In order to more precisely determine the taxonomic position of these isolates, detailed morphological characterizations and multi-locus phylogenetic analyses were performed. Based on these analyses, the isolates were grouped into four main clades: section <i>Ulocladioides</i>, section <i>Infectoriae</i>, including two new species, section <i>Embellisioides</i>, and section <i>Eureka</i>, including one new species. These isolates were also characterized for their virulence under green-house conditions. They were able to produce leaf spot symptoms on tomato plants but with variable levels.