wp_list_authors including custom post types

Add the following function in functions.php and use custom_wp_list_authors function in place of wp_list_authors in your theme where you want to display authors who wrote custom post types post.

function custom_wp_list_authors($args="") {
global $wpdb;

$defaults = array(
    'orderby' => 'name', 'order' => 'ASC', 'number' => '',
    'optioncount' => false, 'exclude_admin' => true,
    'show_fullname' => false, 'hide_empty' => true,
    'feed' => '', 'feed_image' => '', 'feed_type' => '', 'echo' => true,
    'style' => 'list', 'html' => true
);

$args = wp_parse_args( $args, $defaults );
extract( $args, EXTR_SKIP );

$return = '';

$query_args = wp_array_slice_assoc( $args, array( 'orderby', 'order', 'number' ) );
$query_args['fields'] = 'ids';
$authors = get_users( $query_args );

    $custom_post_types = get_post_types(array('_builtin' => false));
    if(!empty($custom_post_types)){
        $temp = implode ("','", $custom_post_types);
        $custom_post_types = "'"; 
        $custom_post_types .= $temp; 
        $custom_post_types .= "','post'";
    }else{
        $custom_post_types .= "'post'";
    }
$author_count = array();        
foreach ( (array) $wpdb->get_results("SELECT DISTINCT post_author, COUNT(ID) AS count FROM $wpdb->posts WHERE post_type in ($custom_post_types)  AND " . get_private_posts_cap_sql( 'post' ) . " GROUP BY post_author") as $row )
    $author_count[$row->post_author] = $row->count;

foreach ( $authors as $author_id ) {
    $author = get_userdata( $author_id );

    if ( $exclude_admin && 'admin' == $author->display_name )
        continue;

    $posts = isset( $author_count[$author->ID] ) ? $author_count[$author->ID] : 0;

    if ( !$posts && $hide_empty )
        continue;

    $link = '';

    if ( $show_fullname && $author->first_name && $author->last_name )
        $name = "$author->first_name $author->last_name";
    else
        $name = $author->display_name;

    if ( !$html ) {
        $return .= $name . ', ';

        continue; // No need to go further to process HTML.
    }

    if ( 'list' == $style ) {
        $return .= '<li>';
    }

    $link = '<a href="' . get_author_posts_url( $author->ID, $author->user_nicename ) . '" title="' . esc_attr( sprintf(__("Posts by %s"), $author->display_name) ) . '">' . $name . '</a>';

    if ( !empty( $feed_image ) || !empty( $feed ) ) {
        $link .= ' ';
        if ( empty( $feed_image ) ) {
            $link .= '(';
        }

        $link .= '<a href="' . get_author_feed_link( $author->ID ) . '"';

        $alt = $title="";
        if ( !empty( $feed ) ) {
            $title=" title="" . esc_attr( $feed ) . '"';
            $alt=" alt="" . esc_attr( $feed ) . '"';
            $name = $feed;
            $link .= $title;
        }

        $link .= '>';

        if ( !empty( $feed_image ) )
            $link .= '<img src="' . esc_url( $feed_image ) . '" style="border: none;"' . $alt . $title . ' />';
        else
            $link .= $name;

        $link .= '</a>';

        if ( empty( $feed_image ) )
            $link .= ')';
    }

    if ( $optioncount )
        $link .= ' ('. $posts . ')';

    $return .= $link;
    $return .= ( 'list' == $style ) ? '</li>' : ', ';
}

$return = rtrim($return, ', ');

if ( !$echo )
    return $return;

echo $return;
}