diff --git a/app/Observers/PrelimDefinitionObserver.php b/app/Observers/PrelimDefinitionObserver.php
new file mode 100644
index 0000000..e66a915
--- /dev/null
+++ b/app/Observers/PrelimDefinitionObserver.php
@@ -0,0 +1,51 @@
+<?php
+
+namespace App\Observers;
+
+use App\Models\PrelimDefinition;
+use App\Models\Room;
+use App\Models\ScoringGuide;
+
+class PrelimDefinitionObserver
+{
+    /**
+     * Handle the PrelimDefinition "created" event.
+     */
+    public function created(PrelimDefinition $prelimDefinition): void
+    {
+        $message = 'Created Prelim for '.$prelimDefinition->audition->name.'.';
+        $affected = ['auditions' => [$prelimDefinition->audition_id]];
+        auditionLog($message, $affected);
+    }
+
+    /**
+     * Handle the PrelimDefinition "updated" event.
+     */
+    public function updated(PrelimDefinition $prelimDefinition): void
+    {
+        $message = 'Updated Prelim for '.$prelimDefinition->audition->name.'.';
+        if ($prelimDefinition->getOriginal('room_id') !== $prelimDefinition->room_id) {
+            $oldRoom = Room::find($prelimDefinition->getOriginal('room_id'));
+            $message .= '<br>Room: '.$oldRoom->name.' -> '.$prelimDefinition->room->name;
+        }
+
+        if ($prelimDefinition->getOriginal('scoring_guide_id') !== $prelimDefinition->scoring_guide_id) {
+            $oldScoringGuide = ScoringGuide::find($prelimDefinition->getOriginal('scoring_guide_id'));
+            $message .= '<br>Scoring Guide: '.$oldScoringGuide->name.' -> '.$prelimDefinition->scoringGuide->name;
+        }
+
+        if ($prelimDefinition->getOriginal('passing_score') !== $prelimDefinition->passing_score) {
+            $message .= '<br>Passing Score: '.$prelimDefinition->getOriginal('passing_score').' -> '.$prelimDefinition->passing_score;
+        }
+        auditionLog($message, ['auditions' => [$prelimDefinition->audition_id]]);
+    }
+
+    /**
+     * Handle the PrelimDefinition "deleted" event.
+     */
+    public function deleted(PrelimDefinition $prelimDefinition): void
+    {
+        $message = 'Deleted Prelim for '.$prelimDefinition->audition->name.'.';
+        auditionLog($message, ['auditions' => [$prelimDefinition->audition_id]]);
+    }
+}
diff --git a/app/Providers/AppServiceProvider.php b/app/Providers/AppServiceProvider.php
index 398ee75..c7288e0 100644
--- a/app/Providers/AppServiceProvider.php
+++ b/app/Providers/AppServiceProvider.php
@@ -12,6 +12,7 @@ use App\Models\BonusScore;
 use App\Models\Entry;
 use App\Models\EntryFlag;
 use App\Models\Event;
+use App\Models\PrelimDefinition;
 use App\Models\School;
 use App\Models\SchoolEmailDomain;
 use App\Models\ScoreSheet;
@@ -23,6 +24,7 @@ use App\Observers\BonusScoreObserver;
 use App\Observers\EntryFlagObserver;
 use App\Observers\EntryObserver;
 use App\Observers\EventObserver;
+use App\Observers\PrelimDefinitionObserver;
 use App\Observers\SchoolEmailDomainObserver;
 use App\Observers\SchoolObserver;
 use App\Observers\ScoreSheetObserver;
@@ -69,6 +71,7 @@ class AppServiceProvider extends ServiceProvider
         EntryFlag::observe(EntryFlagObserver::class);
         Event::observe(EventObserver::class);
         School::observe(SchoolObserver::class);
+        PrelimDefinition::observe(PrelimDefinitionObserver::class);
         SchoolEmailDomain::observe(SchoolEmailDomainObserver::class);
         ScoreSheet::observe(ScoreSheetObserver::class);
         ScoringGuide::observe(ScoringGuideObserver::class);